485BPOS

As filed with the Securities and Exchange Commission on November 19, 2013

Securities Act File No. 333-173276

Investment Company Act of 1940 File No. 811-22542

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	x
Pre-Effective Amendment No.	¨
Post-Effective Amendment No. 15	x

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	x
Amendment No. 21	x

SSgA Active ETF Trust

(Exact Name of Registrant as Specified in Charter)

One Lincoln Street

Boston, Massachusetts 02111

(Address of Principal Executive Offices)

Registrant’s Telephone Number: (866) 787-2257

Christopher A. Madden, Esq.

State Street Bank and Trust Company

One Lincoln Street/CPH0326

Boston, Massachusetts 02111

(Name and Address of Agent for Service)

Copies to:

W. John McGuire, Esq.

Bingham McCutchen LLP

2020 K Street NW

Washington, DC 20006

It is proposed that this filing will become effective:

x immediately upon filing pursuant to Rule 485, paragraph (b)

¨ on             pursuant to Rule 485, paragraph (b)

¨ 60 days after filing pursuant to Rule 485, paragraph (a)(1)

¨ on             pursuant to Rule 485, paragraph (a)(1)

¨ 75 days after filing pursuant to Rule 485, paragraph (a)(2)

¨ on             pursuant to Rule 485, paragraph (a)(2)

¨ As soon as practicable after the effective date of this registration statement.

SSGA MASTER TRUST HAS ALSO EXECUTED THIS REGISTRATION STATEMENT

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this registration statement under Rule 485(b) under the Securities Act and has caused this amendment to the registration statement to be signed on its behalf by the undersigned, duly authorized, in the City of Boston and Commonwealth of Massachusetts on the 19th day of November, 2013.

SSgA Active ETF Trust
By:	/s/ Ellen M. Needham
	Ellen M. Needham President

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, this amendment to the registration statement has been signed below by the following persons in the capacities and on the date indicated:

SIGNATURES	TITLE	DATE
/s/ Bonny E. Boatman*	Trustee	November 19, 2013
Bonny E. Boatman
/s/ Dwight D. Churchill*	Trustee	November 19, 2013
Dwight D. Churchill
/s/ David M. Kelly*	Trustee	November 19, 2013
David M. Kelly
/s/ Frank Nesvet*	Trustee	November 19, 2013
Frank Nesvet
/s/ Carl G. Verboncoeur*	Trustee	November 19, 2013
Carl G. Verboncoeur
/s/ James E. Ross*	Trustee	November 19, 2013
James E. Ross
/s/ Ellen M. Needham Ellen M. Needham	President and Principal Executive Officer	November 19, 2013
/s/ Chad C. Hallett Chad C. Hallett	Treasurer and Principal Financial Officer	November 19, 2013

*By:	/s/ Christopher A. Madden
	Christopher A. Madden
	As Attorney-in-Fact Pursuant to Power of Attorney

SIGNATURES

SSgA Master Trust (the “Trust”), has duly caused this Post-Effective Amendment No. 15 to the Registration Statement on Form N-1A of the SSgA Active ETF Trust (the “Registrant”) to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston and the Commonwealth of Massachusetts on November 19, 2013.

SSGA MASTER TRUST
By:	/s/ Ellen M. Needham
	Ellen M. Needham President

This Registration Statement on Form N-1A of the Registrant has been signed below by the following persons, solely in the capacities indicated, on November 19, 2013.

SIGNATURE	TITLE
/s/ Bonny E. Boatman*	Trustee
Bonny E. Boatman
/s/ Dwight D. Churchill*	Trustee
Dwight D. Churchill
/s/ David M. Kelly*	Trustee
David M. Kelly
/s/ Frank Nesvet*	Trustee
Frank Nesvet
/s/ Carl G. Verboncoeur*	Trustee
Carl G. Verboncoeur
/s/ James E. Ross* James E. Ross	Trustee
/s/ Ellen M. Needham Ellen M. Needham	President and Principal Executive Officer
/s/ Chad C. Hallett	Treasurer and Principal Financial Officer
Chad C. Hallett

*By:	/s/ Christopher A. Madden
	Christopher A. Madden
	As Attorney-in-Fact Pursuant to Power of Attorney

Exhibit Index

Exhibit No.
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Global Allocation ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR® SSgA Global Allocation ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Global Allocation ETF (the “Fund”) seeks to provide capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate (based on the Portfolio’s turnover rate) was 123% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	123.00%
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Global Allocation Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide balanced exposure to domestic and international debt and equity securities. The Portfolio typically allocates approximately 60% of its assets to equity securities, though this percentage can vary based on the Adviser’s tactical decisions. The allocations to each asset class will change over time as the Adviser’s expectations of each asset class shift. The Portfolio’s indirect holdings by virtue of investing in ETPs representing these asset classes consist of a diversified mix of domestic and international, including emerging market, equity securities across all market capitalizations, investment grade and high yield government and corporate bonds, inflation protected securities, mortgage pass through securities, commercial mortgage backed securities, asset backed securities, commodities and real estate investment trusts (“REITs”). The Portfolio, through its investments in ETPs, will generally invest at least 30% of its assets in securities of issuers economically tied to countries other than the United States and will generally hold securities of issuers economically tied to at least three countries, including the United States. In determining if a security is economically tied to a non-U.S. country, the Portfolio generally looks to the country of incorporation of the issuer as listed on Bloomberg, a widely recognized provider of market information. However, the Adviser may determine a security is economically tied to a non-U.S. country based on other factors, such as an issuer’s country of domicile, where more than 50% of an issuer’s revenues are generated or where an issuer’s primary exchange is located. As a result, a security may be economically tied to more than one country. ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); exchange traded commodity trusts; and exchange traded notes (“ETNs”). The Portfolio may invest in ETPs that are qualified publicly traded partnerships (“QPTPs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs: EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income. FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative. COMMODITIES RISK:  Exposure to the commodities markets may subject the Portfolio to greater volatility than investments in traditional securities. Commodities are subject to substantial price fluctuations over short periods of time and may be affected by unpredictable economic, political and environmental events. Factors that may significantly affect the prices of commodities include, but are not limited to: global supply and demand; domestic and international interest rates and investors’ expectations of interest rates; inflation rates and investors’ expectations of inflation rates; the investment and trading activities of commodity futures contracts; political, economic, or financial events, both globally and regionally. TAX RISK:  Regulated investment companies are subject to favorable tax treatment under the Internal Revenue Code. To qualify as a regulated investment company, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. Thus, income from the Portfolio’s investments in certain commodities-related investments may cause the Fund not to qualify as a regulated investment company. The Portfolio may invest up to 25% of its total assets in one or more ETPs that are QPTPs and whose principal activities are the buying and selling of commodities or options, futures, or forwards with respect to commodities. Income from QPTPs is generally qualifying income. If an ETP fails to qualify as a QPTP, the income generated from the Portfolio’s investment in the ETP may not be qualifying income. The Portfolio will only invest in such an ETP if it intends to qualify as a QPTP, but there is no guarantee that each such ETP will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of such ETPs as QPTPs. If the Fund fails to qualify as a regulated investment company, the Fund will be subject to tax, which will reduce returns to shareholders. Such a failure will also alter the treatment of distributions to shareholders. HIGH YIELD SECURITIES RISK:  Securities rated below investment grade, commonly referred to as “junk bonds,” include bonds that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Adviser, and may involve greater risks than securities in higher rating categories. Such bonds are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities without taking a discount, which could be significant. High yield securities also may present greater credit risk because such securities may be issued in connection with corporate restructuring by highly leveraged issuers or may not be current in the payment of interest or principal or in default. U.S. GOVERNMENT AGENCY SECURITIES RISK:  Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, the performance of the Portfolio and, therefore, the Fund will be adversely impacted. PREPAYMENT RISK:  Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income. MORTGAGE-BACKED SECURITIES RISK:  Mortgage-backed securities, other than Government National Mortgage Association (“GNMA”) mortgage-backed securities, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. Mortgage-backed securities tend to increase in value less than other debt securities when interest rates decline, but are subject to similar risk of decline in market value during periods of rising interest rates. Because of prepayment and extension risk, mortgage-backed securities react differently to changes in interest rates than other bonds. Small movements in interest rates (both increases and decreases) may quickly and significantly affect the value of certain mortgage-backed securities. MORTGAGE PASS-THROUGH SECURITIES RISK:  Most transactions in mortgage pass-through securities occur through standardized contracts for future delivery in which the exact mortgage pools to be delivered are not specified until a few days prior to settlement, referred to as a “to-be-announced transaction” or “TBA Transaction.” In a TBA Transaction, the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount and price. Default by or bankruptcy of a counterparty to a TBA Transaction would expose the Portfolio to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA Transaction. REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act. MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Global Allocation ETF | SPDR SSgA Global Allocation ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets	0.35%	[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets	none	[1]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets	0.35%	[1]
YEAR 1	rr_ExpenseExampleYear01	$ 36
YEAR 3	rr_ExpenseExampleYear03	113
YEAR 5	rr_ExpenseExampleYear05	197
YEAR 10	rr_ExpenseExampleYear10	$ 443

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA US Minimum Volatility ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR SSgA US Minimum Volatility ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA US Minimum Volatility ETF (the “Fund”) seeks to provide competitive long-term returns while maintaining low long-term volatility relative to the broad U.S. market.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA US Minimum Volatility Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) utilizes a proprietary quantitative investment process to select a portfolio of equity securities that the Adviser believes will exhibit low long-term volatility and provide competitive long-term returns relative to the broad U.S. market. Volatility is a statistical measurement of the magnitude of up and down fluctuations in the value of a financial instrument or index over time. Volatility may result in rapid and dramatic price swings. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in U.S. investments. The Adviser expects to favor securities with low exposure to market risk factors and low security-specific risk. The Adviser considers market risk factors to include, among others, a security’s size, momentum, value, liquidity, leverage and growth. While the Adviser attempts to manage the Fund’s volatility exposure to stabilize performance, there can be no guarantee that the Fund will reach its target volatility. Additionally, the Adviser implements certain risk constraints at the security, industry, size exposure, and sector levels. Through this quantitative process of security selection and portfolio diversification, the Adviser expects that the portfolio will be subject to a low level of absolute risk (as defined by standard deviation of returns) and thus should exhibit low volatility over the long term.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio’s and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA US Minimum Volatility ETF | SPDR SSgA US Minimum Volatility ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR SSgA Conservative Global Allocation ETF

SPDR^® SSgA Conservative Global Allocation ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Conservative Global Allocation ETF (the “Fund”) seeks to provide current income, capital preservation and the avoidance of excessive portfolio volatility.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Conservative Global Allocation ETF
MANAGEMENT FEES	[1][2]	0.35%
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]	none
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]	0.35%

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Conservative Global Allocation ETF	36	113

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Conservative Global Allocation Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide exposure to domestic and international debt and equity securities with a larger allocation to debt securities than to other asset classes. These fixed income securities tend to be less volatile than traditional equity securities. The Portfolio typically allocates approximately 60% of its assets to debt related securities, though this percentage can vary based on the Adviser’s tactical decisions. The allocations to each asset class will change over time as the Adviser’s expectations of each asset class shift. The Portfolio’s indirect holdings by virtue of investing in ETPs representing these asset classes consist of a diversified mix of domestic and international, including emerging market, equity securities across all market capitalizations, investment grade and high yield government and corporate bonds, inflation protected securities, mortgage pass through securities, commercial mortgage backed securities, asset backed securities, commodities and real estate investment trusts (“REITs”). The Portfolio, through its investments in ETPs, will generally invest at least 30% of its assets in securities of issuers economically tied to countries other than the United States and will generally hold securities of issuers economically tied to at least three countries, including the United States. In determining if a security is economically tied to a non-U.S. country, the Portfolio generally looks to the country of incorporation of the issuer as listed on Bloomberg, a widely recognized provider of market information. However, the Adviser may determine a security is economically tied to a non-U.S. country based on other factors, such as an issuer’s country of domicile, where more than 50% of an issuer’s revenues are generated or where an issuer’s primary exchange is located. As a result, a security may be economically tied to more than one country.

ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); exchange traded commodity trusts; and exchange traded notes (“ETNs”). The Portfolio may invest in ETPs that are qualified publicly traded partnerships (“QPTPs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs:

EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income.

FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative.

COMMODITIES RISK:  Exposure to the commodities markets may subject the Portfolio to greater volatility than investments in traditional securities. Commodities are subject to substantial price fluctuations over short periods of time and may be affected by unpredictable economic, political and environmental events. Factors that may significantly affect the prices of commodities include, but are not limited to: global supply and demand; domestic and international interest rates and investors’ expectations of interest rates; inflation rates and investors’ expectations of inflation rates; the investment and trading activities of commodity futures contracts; political, economic, or financial events, both globally and regionally.

TAX RISK:  Regulated investment companies are subject to favorable tax treatment under the Internal Revenue Code. To qualify as a regulated investment company, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. Thus, income from the Portfolio’s investments in certain commodities-related investments may cause the Fund not to qualify as a regulated investment company. The Portfolio may invest up to 25% of its total assets in one or more ETPs that are QPTPs and whose principal activities are the buying and selling of commodities or options, futures, or forwards with respect to commodities. Income from QPTPs is generally qualifying income. If an ETP fails to qualify as a QPTP, the income generated from the Portfolio’s investment in the ETP may not be qualifying income. The Portfolio will only invest in such an ETP if it intends to qualify as a QPTP, but there is no guarantee that each such ETP will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of such ETPs as QPTPs. If the Fund fails to qualify as a regulated investment company, the Fund will be subject to tax, which will reduce returns to shareholders. Such a failure will also alter the treatment of distributions to shareholders.

HIGH YIELD SECURITIES RISK:  Securities rated below investment grade, commonly referred to as “junk bonds,” include bonds that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Adviser, and may involve greater risks than securities in higher rating categories. Such bonds are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities without taking a discount, which could be significant. High yield securities also may present greater credit risk because such securities may be issued in connection with corporate restructuring by highly leveraged issuers or may not be current in the payment of interest or principal or in default.

U.S. GOVERNMENT AGENCY SECURITIES RISK:  Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, the performance of the Portfolio and, therefore, the Fund will be adversely impacted.

PREPAYMENT RISK:  Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income.

MORTGAGE-BACKED SECURITIES RISK:  Mortgage-backed securities, other than Government National Mortgage Association (“GNMA”) mortgage-backed securities, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. Mortgage-backed securities tend to increase in value less than other debt securities when interest rates decline, but are subject to similar risk of decline in market value during periods of rising interest rates. Because of prepayment and extension risk, mortgage-backed securities react differently to changes in interest rates than other bonds. Small movements in interest rates (both increases and decreases) may quickly and significantly affect the value of certain mortgage-backed securities.

MORTGAGE PASS-THROUGH SECURITIES RISK:  Most transactions in mortgage pass-through securities occur through standardized contracts for future delivery in which the exact mortgage pools to be delivered are not specified until a few days prior to settlement, referred to as a “to-be-announced transaction” or “TBA Transaction.” In a TBA Transaction, the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount and price. Default by or bankruptcy of a counterparty to a TBA Transaction would expose the Portfolio to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA Transaction.

REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act.

MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.

FUND PERFORMANCE

The Fund has not commenced operations as of the date of this Prospectus and therefore the Fund does not have a full calendar year of performance information.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR SSgA Aggressive Global Allocation ETF

SPDR^® SSgA Aggressive Global Allocation ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Aggressive Global Allocation ETF (the “Fund”) seeks to provide capital appreciation,

with a secondary emphasis on current income.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Aggressive Global Allocation ETF
MANAGEMENT FEES	[1][2]	0.35%
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]	none
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]	0.35%

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Aggressive Global Allocation ETF	36	113

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Aggressive Global Allocation Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide exposure to domestic and international debt and equity securities with a larger allocation to equity securities than to other asset classes. These equity securities tend to be more volatile than traditional fixed income securities. The Portfolio typically allocates approximately 80% or more of its assets to equity securities, though this percentage can vary based on the Adviser’s tactical decisions. The Portfolio’s indirect holdings by virtue of investing in ETPs representing these asset classes consist of a diversified mix of domestic and international, including emerging market, equity securities across all market capitalizations, investment grade and high yield government and corporate bonds, inflation protected securities, mortgage pass through securities, commercial mortgage backed securities, asset backed securities, commodities and real estate investment trusts (“REITs”). The Portfolio, through its investments in ETPs, will generally invest at least 30% of its assets in securities of issuers economically tied to countries other than the United States and will generally hold securities of issuers economically tied to at least three countries, including the United States. In determining if a security is economically tied to a non-U.S. country, the Portfolio generally looks to the country of incorporation of the issuer as listed on Bloomberg, a widely recognized provider of market information. However, the Adviser may determine a security is economically tied to a non-U.S. country based on other factors, such as an issuer’s country of domicile, where more than 50% of an issuer’s revenues are generated or where an issuer’s primary exchange is located. As a result, a security may be economically tied to more than one country.

ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); exchange traded commodity trusts; and exchange traded notes (“ETNs”). The Portfolio may invest in ETPs that are qualified publicly traded partnerships (“QPTPs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs:

EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income.

FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative.

COMMODITIES RISK:  Exposure to the commodities markets may subject the Portfolio to greater volatility than investments in traditional securities. Commodities are subject to substantial price fluctuations over short periods of time and may be affected by unpredictable economic, political and environmental events. Factors that may significantly affect the prices of commodities include, but are not limited to: global supply and demand; domestic and international interest rates and investors’ expectations of interest rates; inflation rates and investors’ expectations of inflation rates; the investment and trading activities of commodity futures contracts; political, economic, or financial events, both globally and regionally.

TAX RISK:  Regulated investment companies are subject to favorable tax treatment under the Internal Revenue Code. To qualify as a regulated investment company, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. Thus, income from the Portfolio’s investments in certain commodities-related investments may cause the Fund not to qualify as a regulated investment company. The Portfolio may invest up to 25% of its total assets in one or more ETPs that are QPTPs and whose principal activities are the buying and selling of commodities or options, futures, or forwards with respect to commodities. Income from QPTPs is generally qualifying income. If an ETP fails to qualify as a QPTP, the income generated from the Portfolio’s investment in the ETP may not be qualifying income. The Portfolio will only invest in such an ETP if it intends to qualify as a QPTP, but there is no guarantee that each such ETP will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of such ETPs as QPTPs. If the Fund fails to qualify as a regulated investment company, the Fund will be subject to tax, which will reduce returns to shareholders. Such a failure will also alter the treatment of distributions to shareholders.

HIGH YIELD SECURITIES RISK:  Securities rated below investment grade, commonly referred to as “junk bonds,” include bonds that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Adviser, and may involve greater risks than securities in higher rating categories. Such bonds are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities without taking a discount, which could be significant. High yield securities also may present greater credit risk because such securities may be issued in connection with corporate restructuring by highly leveraged issuers or may not be current in the payment of interest or principal or in default.

U.S. GOVERNMENT AGENCY SECURITIES RISK:  Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, the performance of the Portfolio and, therefore, the Fund will be adversely impacted.

PREPAYMENT RISK:  Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income.

MORTGAGE-BACKED SECURITIES RISK:  Mortgage-backed securities, other than Government National Mortgage Association (“GNMA”) mortgage-backed securities, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. Mortgage-backed securities tend to increase in value less than other debt securities when interest rates decline, but are subject to similar risk of decline in market value during periods of rising interest rates. Because of prepayment and extension risk, mortgage-backed securities react differently to changes in interest rates than other bonds. Small movements in interest rates (both increases and decreases) may quickly and significantly affect the value of certain mortgage-backed securities.

MORTGAGE PASS-THROUGH SECURITIES RISK:  Most transactions in mortgage pass-through securities occur through standardized contracts for future delivery in which the exact mortgage pools to be delivered are not specified until a few days prior to settlement, referred to as a “to-be-announced transaction” or “TBA Transaction.” In a TBA Transaction, the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount and price. Default by or bankruptcy of a counterparty to a TBA Transaction would expose the Portfolio to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA Transaction.

REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act.

MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.

FUND PERFORMANCE

The Fund has not commenced operations as of the date of this Prospectus and therefore the Fund does not have a full calendar year of performance information.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Global Minimum Volatility ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR SSgA Global Minimum Volatility ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Global Minimum Volatility ETF (the “Fund”) seeks to provide competitive long-term returns while maintaining low long-term volatility relative to the broad global market.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Global Minimum Volatility Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) utilizes a proprietary quantitative investment process to select a portfolio of equity securities that the Adviser believes will exhibit low volatility and provide competitive long-term returns relative to the broad global market. Volatility is a statistical measurement of the magnitude of up and down fluctuations in the value of a financial instrument or index over time. Volatility may result in rapid and dramatic price swings. The Portfolio will invest its assets in both U.S. and foreign investments. The Portfolio will generally invest at least 30% of its assets in securities of issuers economically tied to countries other than the United States and will generally hold securities of issuers economically tied to at least three countries, including the United States. The Adviser expects to favor securities with low exposure to market risk factors and low security-specific risk. The Adviser considers market risk factors to include, among others, a security’s size, momentum, value, liquidity, leverage and growth. While the Adviser attempts to manage the Fund’s volatility exposure to stabilize performance, there can be no guarantee that the Fund will reach its target volatility. Additionally, the Adviser implements risk constraints at the security, industry, size exposure, and sector levels. Through this quantitative process of security selection and portfolio diversification, the Adviser expects that the portfolio will be subject to a low level of absolute risk (as defined by standard deviation of returns) and thus should exhibit low volatility over the long term.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market. FOREIGN INVESTMENT RISK: Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. EMERGING MARKETS RISK: Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shut down, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio’s and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Global Minimum Volatility ETF | SPDR SSgA Global Minimum Volatility ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR SSgA Small Cap Risk Aware ETF

SPDR SSgA Small Cap Risk Aware ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Small Cap Risk Aware ETF (the “Fund”) seeks to provide competitive returns compared to the small cap U.S. equity market and capital appreciation.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Small Cap Risk Aware ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Small Cap Risk Aware ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Small Cap Risk Aware Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

In seeking its objective, the Portfolio invests in a diversified selection of equity securities included in the Russell 2000 Index that SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) believes are aligned with predicted investor risk preferences. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in securities of small-cap companies. The Portfolio considers small-cap companies to be companies with market capitalizations falling within the range of the Russell 2000 Index at the time of initial purchase. In selecting securities for the Portfolio, the Adviser utilizes a proprietary quantitative investment process to measure and predict investor risk preferences. This process reflects the multidimensional and time-varying nature of risk, as stock characteristics the market deems to be safe or risky change over time. As a result, different periods of predicted uncertainty may result in portfolios that are more defensive or risk-seeking, depending on what the market considers safe and/or risky at each juncture (in light of factors such as beta, size, credit risk, credit spreads, exposure to gold, U.S. dollar exchange rates, and implied volatility). During periods of anticipated high risk, the Adviser will adjust the Portfolio’s composition to be defensive and may increase exposure to value companies. During periods of anticipated low risk, the Adviser will adjust the Portfolio’s composition to be risk-seeking and may increase exposure to growth companies. In periods of anticipated moderate risk, the Portfolio’s composition will more closely reflect the weighted composition of the Russell 2000 Index. Due to on-going market fluctuations, the Adviser believes the resulting ebbing and flowing of risk preferences give this strategy the potential to provide competitive returns relative to the Russell 2000 Index over the long term. The Portfolio is non-diversified for purposes of the Investment Company Act of 1940, and as a result may invest a greater percentage of its assets in a particular issuer than a diversified fund. However, the Portfolio expects to have exposure to a diversified mix of equity securities.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general.

FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market.

SMALL CAP RISK: Small-sized companies may be more volatile and more likely than large- and mid-capitalization companies to have relatively limited product lines, markets or financial resources, or depend on a few key employees. Returns on investments in stocks of small companies could trail the returns on investments in stocks of larger companies.

GROWTH RISK: The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on “growth” securities may or may not move in tandem with the returns on other styles of investing or the overall stock market.

VALUE RISK: A “value” style of investing emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR SSgA Ultra Short Term Bond ETF

SPDR^® SSgA Ultra Short Term Bond ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Ultra Short Term Bond ETF (the “Fund”) seeks to provide current income consistent with preservation of capital and daily liquidity through short duration high quality investments.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Ultra Short Term Bond ETF
MANAGEMENT FEES	[1][2]	0.20%
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]	none
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]	0.20%

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Ultra Short Term Bond ETF	20	64

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Ultra Short Term Bond Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests, under normal circumstances, at least 80% of the Portfolio’s net assets (plus the amount of borrowings for investment purposes) in a diversified portfolio of U.S. dollar-denominated investment grade fixed income securities. The Portfolio primarily invests in investment grade fixed income securities that are rated at the time of purchase a minimum of A- or higher by Standard & Poor’s Financial Services LLC and/or Fitch Inc., or A3 or higher by Moody’s Investors Service, Inc., or, if unrated, determined by the management team to be of equivalent quality. The Portfolio invests in fixed and floating rate securities of varying maturities, such as corporate obligations (including commercial paper of U.S. and foreign entities, master notes, and medium term notes); government bonds (including U.S. Treasury Bills, notes, and bonds); agency securities; privately-issued securities; asset-backed and mortgage-backed securities; money market instruments (including U.S. and foreign bank time deposits, certificates of deposit, and banker acceptances) and other investment companies. The Portfolio may also invest in exchange traded products (“ETPs”). ETPs include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”) and exchange traded notes (“ETNs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.

Under normal circumstances, the effective duration of the Portfolio is expected to be between three and nine months. Effective duration is a measure of the Portfolio’s price sensitivity to changes in yields or interest rates; however, investors should be aware that effective duration is not an exact measurement and may not reliably predict a particular security’s price sensitivity to changes in yield or interest rates. In addition, the Portfolio expects to maintain a weighted average maturity between six and eighteen months. Weighted average maturity is a U.S. dollar-weighted average of the remaining term to maturity of the underlying securities in the Portfolio. For the purposes of determining the Portfolio’s weighted average maturity, a security’s final maturity date, or for amortizing securities such as asset-backed and mortgage-backed securities, its weighted average life will be used for calculation purposes. The Adviser buys and sells securities for the Portfolio based on its analysis of credit quality and overall portfolio duration. A security will generally be sold from the Portfolio where the Adviser believes that a different security, viewed in light of its maturity, provides a higher yield. The Portfolio and Fund are not money market funds and do not seek to maintain a stable net asset value of $1.00 per share.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

DEBT SECURITIES INVESTING RISK:  The value of debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income.

FLOATING RATE NOTES INVESTING RISK:  Floating rate notes protect investors against a rise in interest rates, but also carry lower yields than fixed notes of the same maturity. The interest rate for a floating rate note resets or adjusts periodically (normally on a daily, monthly, quarterly or semiannual basis by reference to a base lending rate (such as LIBOR). Because rates on floating rate notes reset only periodically, changes in prevailing interest rates (particularly sudden and significant changes) can be expected to cause fluctuations in net asset value. Floating rate notes generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Portfolio needs to liquidate such loans.

U.S. TREASURY OBLIGATIONS RISK:  Treasury obligations may differ from other fixed income securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the United States may cause the value of its Treasury obligations to decline.

U.S. GOVERNMENT AGENCY SECURITIES RISK:  Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, performance will be adversely impacted.

SOVEREIGN OBLIGATIONS RISK:  The Portfolio invests in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations.

ASSET-BACKED AND MORTGAGE-BACKED SECURITIES RISK:  Asset-backed and mortgage-backed securities (residential and commercial) represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. These securities, in most cases, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. These securities are subject to the risk of default on the underlying asset or mortgage, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities.

PREPAYMENT RISK:  Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income.

PRIVATELY-ISSUED SECURITIES RISK:  The Portfolio will invest in privately-issued securities, including those which are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act. Privately-issued securities are securities that have not been registered under the Securities Act and as a result are subject to legal restrictions on resale. Privately-issued securities are not traded on established markets and may be illiquid, difficult to value and subject to wide fluctuations in value. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Portfolio from disposing of them promptly at reasonable prices.

FOREIGN INVESTMENT RISK:  Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the U.S. pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; different practices for clearing and settling trades; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of the currency of the country in which the Fund has invested could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

FINANCIAL SECTOR RISK:  Financial services companies are subject to extensive governmental regulation which may limit both the amounts and types of loans and other financial commitments they can make, and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change or due to increased competition. In addition, the recent deterioration of the credit markets generally has caused an adverse impact in a broad range of markets, including U.S. and international credit and interbank money markets generally, thereby affecting a wide range of financial institutions and markets. Recent events in the financial sector have resulted, and may continue to result, in an unusually high degree of volatility in the financial markets, both domestic and foreign, and cause certain financial services companies to incur large losses. Numerous financial services companies have experienced substantial declines in the valuations of their assets, taken action to raise capital (such as the issuance of debt or equity securities), or even ceased operations. These actions have caused the securities of many financial services companies to experience a dramatic decline in value. Credit losses resulting from financial difficulties of borrowers and financial losses associated with investment activities can negatively impact the sector. Insurance companies may be subject to severe price competition.

EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investment in ETPs:

AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.

MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

NON-DIVERSIFICATION RISK:  The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.

PORTFOLIO TURNOVER RISK:  The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad-based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

SPDR SSgA Aggressive Ultra Short Bond ETF

SPDR SSgA Aggressive Ultra Short Term Bond ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Aggressive Ultra Short Term Bond ETF (the “Fund”) seeks to maximize income consistent with preservation of capital through short duration high quality investments.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Aggressive Ultra Short Bond ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Aggressive Ultra Short Bond ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Aggressive Ultra Short Term Bond Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests, under normal circumstances, at least 80% of the Portfolio’s net assets (plus the amount of borrowings for investment purposes) in a diversified portfolio of U.S. dollar-denominated investment grade fixed income securities. The Portfolio primarily invests in investment grade fixed income securities that are rated a minimum of BBB- or higher by Standard & Poor’s Financial Services LLC and/or Fitch Inc., or Baa3 or higher by Moody’s Investors Service, Inc., or, if unrated, determined by the management team to be of equivalent quality. The Portfolio invests in fixed and floating rate securities of varying maturities, such as corporate obligations (including commercial paper of U.S. and foreign entities, master notes, and medium term notes); government bonds (including U.S. Treasury Bills, notes, and bonds); agency securities; privately-issued securities; asset-backed and mortgage-backed securities; money market instruments (including U.S. and foreign bank time deposits, certificates of deposit, and banker acceptances) and other investment companies. The Portfolio may also invest in exchange traded products (“ETPs”). ETPs include exchange traded funds registered under the Investment Company Act of 1940, as amended, (the “1940 Act”) that seek to track the performance of a market index (“Underlying ETFs”) and exchange traded notes. In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.

Under normal circumstances, the effective duration of the Portfolio is expected to be between six and twelve months. Effective duration is a measure of the Portfolio’s price sensitivity to changes in yields or interest rates; however, investors should be aware that effective duration is not an exact measurement and may not reliably predict a particular security’s price sensitivity to changes in yield or interest rates. In addition, the Portfolio expects to maintain a weighted average maturity between 1.5 and 2.5 years. Weighted average maturity is a U.S. dollar-weighted average of the remaining term to maturity of the underlying securities in the Portfolio. For the purposes of determining the Portfolio’s weighted average maturity, a security’s final maturity date, or for amortizing securities such as asset-backed and mortgage-backed securities, its weighted average life will be used for calculation purposes. The Portfolio and Fund are not money market funds and do not seek to maintain a stable net asset value of $1.00 per share.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

DEBT SECURITIES INVESTING RISK: The value of debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income.

FLOATING RATE NOTES INVESTING RISK: Floating rate notes protect investors against a rise in interest rates, but also carry lower yields than fixed notes of the same maturity. The interest rate for a floating rate note resets or adjusts periodically (normally on a daily, monthly, quarterly or semiannual basis by reference to a base lending rate (such as LIBOR). Because rates on floating rate notes reset only periodically, changes in prevailing interest rates (particularly sudden and significant changes) can be expected to cause fluctuations in net asset value. Floating rate notes generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Portfolio needs to liquidate such loans.

U.S. TREASURY OBLIGATIONS RISK: Treasury obligations may differ from other fixed income securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the United States may cause the value of its Treasury obligations to decline.

U.S. GOVERNMENT AGENCY SECURITIES RISK: Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, performance will be adversely impacted.

SOVEREIGN OBLIGATIONS RISK: The Portfolio invests in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations.

ASSET-BACKED AND MORTGAGE-BACKED SECURITIES RISK: Asset-backed and mortgage-backed securities (residential and commercial) represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. These securities, in most cases, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. These securities are subject to the risk of default on the underlying asset or mortgage, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities.

PREPAYMENT RISK: Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income.

PRIVATELY-ISSUED SECURITIES RISK. The Portfolio will invest in privately-issued securities, including those which are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act of 1933, as amended (the “1933 Act”). Privately-issued securities are securities that have not been registered under the 1933 Act and as a result are subject to legal restrictions on resale. Privately-issued securities are not traded on established markets and may be illiquid, difficult to value and subject to wide fluctuations in value. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Portfolio from disposing of them promptly at reasonable prices.

DERIVATIVES RISK: A derivative is a financial contract the value of which depends on, or is derived from, the value of a financial asset (such as stock, bond or currency), a physical asset (such as gold) or a market index (such as the S&P 500 Index). The Fund may invest in forward foreign currency contracts. Forward foreign currency contracts involve an obligation to purchase or sell a specific amount of currency at a future date or date range at a specific price, thereby fixing the exchange rate for a specified time in the future. When used for hedging purposes, forward foreign currency contracts tend to limit any potential gain that may be realized if the value of the Fund’s foreign holdings increases because of currency fluctuations. Compared to conventional securities, derivatives can be more sensitive to changes in interest rates or to sudden fluctuations in market prices and thus the Fund’s losses may be greater if it invests in derivatives than if it invests only in conventional securities.

FOREIGN INVESTMENT RISK: Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

FINANCIAL SECTOR RISK: Financial services companies are subject to extensive governmental regulation which may limit both the amounts and types of loans and other financial commitments they can make, and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change or due to increased competition. In addition, the recent deterioration of the credit markets generally has caused an adverse impact in a broad range of markets, including U.S. and international credit and interbank money markets generally, thereby affecting a wide range of financial institutions and markets. Recent events in the financial sector have resulted, and may continue to result, in an unusually high degree of volatility in the financial markets, both domestic and foreign, and cause certain financial services companies to incur large losses. Numerous financial services companies have experienced substantial declines in the valuations of their assets, taken action to raise capital (such as the issuance of debt or equity securities), or even ceased operations. These actions have caused the securities of many financial services companies to experience a dramatic decline in value. Credit losses resulting from financial difficulties of borrowers and financial losses associated with investment activities can negatively impact the sector. Insurance companies may be subject to severe price competition.

EXCHANGE TRADED PRODUCTS RISK: The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an exchange traded note (“ETN”) may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs:

AFFILIATED ETP RISK: The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

NON-DIVERSIFICATION RISK: The Fund is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio’s and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

SPDR SSgA Large Cap Risk Aware ETF

SPDR SSgA Large Cap Risk Aware ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Large Cap Risk Aware ETF (the “Fund”) seeks to provide competitive returns compared to the large cap U.S. equity market and capital appreciation.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Large Cap Risk Aware ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Large Cap Risk Aware ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Large Cap Risk Aware Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

In seeking its objective, the Portfolio invests in a diversified selection of equity securities included in the Russell 1000 Index that SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) believes are aligned with predicted investor risk preferences. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in securities of large-cap companies. The Portfolio considers large-cap companies to be companies with market capitalizations falling within the range of the Russell 1000 Index at the time of initial purchase. In selecting securities for the Portfolio, the Adviser utilizes a proprietary quantitative investment process to measure and predict investor risk preferences. This process reflects the multidimensional and time-varying nature of risk, as stock characteristics the market deems to be safe or risky change over time. As a result, different periods of predicted uncertainty may result in portfolios that are more defensive or risk-seeking, depending on what the market considers safe and/or risky at each juncture (in light of factors such as beta, size, credit risk, credit spreads, exposure to gold, U.S. dollar exchange rates, and implied volatility). During periods of anticipated high risk, the Adviser will adjust the Portfolio’s composition to be defensive and may increase exposure to value companies. During periods of anticipated low risk, the Adviser will adjust the Portfolio’s composition to be risk-seeking and may increase exposure to growth companies. In periods of anticipated moderate risk, the Portfolio’s composition will more closely reflect the weighted composition of the Russell 1000 Index. Due to on-going market fluctuations, the Adviser believes the resulting ebbing and flowing of risk preferences give this strategy the potential to provide competitive returns relative to the Russell 1000 Index over the long term. The Portfolio is non-diversified for purposes of the Investment Company Act of 1940, and as a result may invest a greater percentage of its assets in a particular issuer than a diversified fund. However, the Portfolio expects to have exposure to a diversified mix of equity securities.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general.

FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market.

LARGE CAP RISK: Returns on investments in stocks of large companies could trail the returns on investments in stocks of smaller and mid-sized companies.

GROWTH RISK: The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on “growth” securities may or may not move in tandem with the returns on other styles of investing or the overall stock market.

VALUE RISK: A “value” style of investing emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Aggressive Ultra Short Bond ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR SSgA Aggressive Ultra Short Term Bond ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Aggressive Ultra Short Term Bond ETF (the “Fund”) seeks to maximize income consistent with preservation of capital through short duration high quality investments.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Aggressive Ultra Short Term Bond Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests, under normal circumstances, at least 80% of the Portfolio’s net assets (plus the amount of borrowings for investment purposes) in a diversified portfolio of U.S. dollar-denominated investment grade fixed income securities. The Portfolio primarily invests in investment grade fixed income securities that are rated a minimum of BBB- or higher by Standard & Poor’s Financial Services LLC and/or Fitch Inc., or Baa3 or higher by Moody’s Investors Service, Inc., or, if unrated, determined by the management team to be of equivalent quality. The Portfolio invests in fixed and floating rate securities of varying maturities, such as corporate obligations (including commercial paper of U.S. and foreign entities, master notes, and medium term notes); government bonds (including U.S. Treasury Bills, notes, and bonds); agency securities; privately-issued securities; asset-backed and mortgage-backed securities; money market instruments (including U.S. and foreign bank time deposits, certificates of deposit, and banker acceptances) and other investment companies. The Portfolio may also invest in exchange traded products (“ETPs”). ETPs include exchange traded funds registered under the Investment Company Act of 1940, as amended, (the “1940 Act”) that seek to track the performance of a market index (“Underlying ETFs”) and exchange traded notes. In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services. Under normal circumstances, the effective duration of the Portfolio is expected to be between six and twelve months. Effective duration is a measure of the Portfolio’s price sensitivity to changes in yields or interest rates; however, investors should be aware that effective duration is not an exact measurement and may not reliably predict a particular security’s price sensitivity to changes in yield or interest rates. In addition, the Portfolio expects to maintain a weighted average maturity between 1.5 and 2.5 years. Weighted average maturity is a U.S. dollar-weighted average of the remaining term to maturity of the underlying securities in the Portfolio. For the purposes of determining the Portfolio’s weighted average maturity, a security’s final maturity date, or for amortizing securities such as asset-backed and mortgage-backed securities, its weighted average life will be used for calculation purposes. The Portfolio and Fund are not money market funds and do not seek to maintain a stable net asset value of $1.00 per share.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. DEBT SECURITIES INVESTING RISK: The value of debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income. FLOATING RATE NOTES INVESTING RISK: Floating rate notes protect investors against a rise in interest rates, but also carry lower yields than fixed notes of the same maturity. The interest rate for a floating rate note resets or adjusts periodically (normally on a daily, monthly, quarterly or semiannual basis by reference to a base lending rate (such as LIBOR). Because rates on floating rate notes reset only periodically, changes in prevailing interest rates (particularly sudden and significant changes) can be expected to cause fluctuations in net asset value. Floating rate notes generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Portfolio needs to liquidate such loans. U.S. TREASURY OBLIGATIONS RISK: Treasury obligations may differ from other fixed income securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the United States may cause the value of its Treasury obligations to decline. U.S. GOVERNMENT AGENCY SECURITIES RISK: Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, performance will be adversely impacted. SOVEREIGN OBLIGATIONS RISK: The Portfolio invests in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations. ASSET-BACKED AND MORTGAGE-BACKED SECURITIES RISK: Asset-backed and mortgage-backed securities (residential and commercial) represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. These securities, in most cases, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. These securities are subject to the risk of default on the underlying asset or mortgage, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities. PREPAYMENT RISK: Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income. PRIVATELY-ISSUED SECURITIES RISK. The Portfolio will invest in privately-issued securities, including those which are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act of 1933, as amended (the “1933 Act”). Privately-issued securities are securities that have not been registered under the 1933 Act and as a result are subject to legal restrictions on resale. Privately-issued securities are not traded on established markets and may be illiquid, difficult to value and subject to wide fluctuations in value. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Portfolio from disposing of them promptly at reasonable prices. DERIVATIVES RISK: A derivative is a financial contract the value of which depends on, or is derived from, the value of a financial asset (such as stock, bond or currency), a physical asset (such as gold) or a market index (such as the S&P 500 Index). The Fund may invest in forward foreign currency contracts. Forward foreign currency contracts involve an obligation to purchase or sell a specific amount of currency at a future date or date range at a specific price, thereby fixing the exchange rate for a specified time in the future. When used for hedging purposes, forward foreign currency contracts tend to limit any potential gain that may be realized if the value of the Fund’s foreign holdings increases because of currency fluctuations. Compared to conventional securities, derivatives can be more sensitive to changes in interest rates or to sudden fluctuations in market prices and thus the Fund’s losses may be greater if it invests in derivatives than if it invests only in conventional securities. FOREIGN INVESTMENT RISK: Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. FINANCIAL SECTOR RISK: Financial services companies are subject to extensive governmental regulation which may limit both the amounts and types of loans and other financial commitments they can make, and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change or due to increased competition. In addition, the recent deterioration of the credit markets generally has caused an adverse impact in a broad range of markets, including U.S. and international credit and interbank money markets generally, thereby affecting a wide range of financial institutions and markets. Recent events in the financial sector have resulted, and may continue to result, in an unusually high degree of volatility in the financial markets, both domestic and foreign, and cause certain financial services companies to incur large losses. Numerous financial services companies have experienced substantial declines in the valuations of their assets, taken action to raise capital (such as the issuance of debt or equity securities), or even ceased operations. These actions have caused the securities of many financial services companies to experience a dramatic decline in value. Credit losses resulting from financial difficulties of borrowers and financial losses associated with investment activities can negatively impact the sector. Insurance companies may be subject to severe price competition. EXCHANGE TRADED PRODUCTS RISK: The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an exchange traded note (“ETN”) may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs: AFFILIATED ETP RISK: The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. NON-DIVERSIFICATION RISK: The Fund is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio’s and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	NON-DIVERSIFICATION RISK: The Fund is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Aggressive Ultra Short Bond ETF | SPDR SSgA Aggressive Ultra Short Bond ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR MFS Systematic Value Equity ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR MFS Systematic Value Equity ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR MFS Systematic Value Equity ETF’s (the “Fund”) investment objective is to seek capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA MFS Systematic Value Equity Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in equity securities. Equity securities in which the Portfolio invests include common stocks, preferred stocks and securities convertible into stocks. In selecting securities for the Portfolio, Massachusetts Financial Services Company (the “Sub-Adviser” or “MFS”) utilizes a bottom-up approach to buying and selling investments for the Portfolio. Investments are selected based on fundamental and quantitative analysis. MFS uses fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions to identify potential investments. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS then uses quantitative models that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors to determine which investments to buy and sell. While the Sub-Adviser may invest the Portfolio’s assets in companies of any size, the Sub-Adviser generally focuses on companies with large market capitalizations. In selecting investments for the Portfolio, the Sub-Adviser invests the Portfolio’s assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies).
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. PREFERRED SECURITIES RISK: Generally, preferred security holders (such as the Portfolio) have no voting rights with respect to the issuing company unless certain events occur. In addition, preferred securities are subordinated to bonds and other debt instruments in a company’s capital structure and therefore will be subject to greater credit risk than those debt instruments. Unlike debt securities, dividend payments on a preferred security typically must be declared by the issuer’s board of directors. An issuer’s board of directors is generally not under any obligation to pay a dividend (even if such dividends have accrued), and may suspend payment of dividends on preferred securities at any time. In the event an issuer of preferred securities experiences economic difficulties, the issuer’s preferred securities may lose substantial value due to the reduced likelihood that the issuer’s board of directors will declare a dividend and the fact that the preferred security may be subordinated to other securities of the same issuer. There is a chance that the issuer of any of the Portfolio’s holdings will default (fail to make scheduled dividend payments on the preferred security or scheduled interest payments on other obligations of the issuer not held by the Portfolio). CONVERTIBLE SECURITIES RISK: Convertible securities are bonds, debentures, notes, preferred stocks or other securities that may be converted or exchanged (by the holder or by the issuer) into shares of the underlying common stock (or cash or securities of equivalent value) at a stated exchange ratio. Convertible securities tend to be subordinate to other debt securities issued by the same issuer so such securities may not receive full repayment in the event of an issuer default. Also, issuers of convertible securities are often not as strong financially as issuers with higher credit ratings. Convertible securities generally provide yields higher than the underlying stocks, but generally lower than comparable non-convertible securities. Because of this higher yield, convertible securities generally sell at a price above their “conversion value,” which is the current market value of the stock to be received upon conversion. The difference between this conversion value and the price of convertible securities will vary over time depending on changes in the value of the underlying common stocks and interest rates. COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general. VALUE RISK: The Portfolio employs a “value” style of investing that emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market. LARGE CAP RISK: Returns on investments in stocks of large U.S. companies could trail the returns on investments in stocks of smaller and mid-sized companies. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Sub-Adviser’s investment strategy may not produce the intended results and may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR MFS Systematic Value Equity ETF | SPDR MFS Systematic Value Equity ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR Blackstone / GSO Senior Loan ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR® Blackstone/GSO Senior Loan ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the SPDR Blackstone/GSO Senior Loan ETF (the “Fund”) is to provide current income consistent with the preservation of capital.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the period from the commencement of the Fund’s operations (April 3, 2013) to the end of the most recent fiscal year, the Fund’s portfolio turnover rate was 4% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	4.00%
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the Blackstone/GSO Senior Loan Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. In pursuing its investment objective, the Portfolio seeks to outperform the Markit iBoxx USD Liquid Leveraged Loan Index (the “Primary Index”) and the S&P/LSTA U.S. Leveraged Loan 100 Index (the “Secondary Index”) by normally investing at least 80% of its net assets (plus any borrowings for investment purposes) in Senior Loans. For purposes of this 80% test, “Senior Loans” are first lien senior secured floating rate bank loans. A Senior Loan is an advance or commitment of funds made by one or more banks or similar financial institutions, including the Portfolio, to one or more corporations, partnerships or other business entities and pays interest at a floating or adjusting rate that is determined periodically at a designated premium above a base lending rate, most commonly the London Interbank Offered Rate (“LIBOR”). A Senior Loan is senior to all unsecured claims against the borrower and senior or equal to all other secured claims, meaning that, in the event of a bankruptcy, the Senior Loan, together with other first lien claims, is entitled to be the first to be repaid out of proceeds of the assets securing the loans, before other existing claims or interests receive repayment. However, in bankruptcy proceedings, there may be other claims, such as taxes or additional advances that take precedence. The Primary Index is composed of the 100 most liquid Senior Loans in the market, while the Secondary Index is composed of the 100 largest Senior Loans in the market, as measured by the borrowed amounts outstanding. The Portfolio intends to hold a large percentage of the components of the Primary and Secondary Indexes. It is anticipated that the Portfolio will invest approximately 50% to 75% of its net assets in Senior Loans that are eligible for inclusion in the Primary and/or Secondary Indexes. Each of the Portfolio’s Senior Loan investments is expected to have no less than $250 million par outstanding. The Portfolio invests in Senior Loans that are made predominantly to businesses operating in North America, but may also invest in Senior Loans made to businesses operating outside of North America. The Portfolio may invest in Senior Loans directly, either from the borrower as part of a primary issuance or in the secondary market through assignments of portions of Senior Loans from third parties, or participations in Senior Loans, which are contractual relationships with an existing lender in a loan facility whereby the Portfolio purchases the right to receive principal and interest payments on a loan but the existing lender remains the record holder of the loan. Under normal market conditions, the Portfolio expects to maintain an average duration of less than 90 days. In selecting securities for the Portfolio, the Portfolio’s sub-adviser, GSO/Blackstone Debt Funds Management LLC (the “Sub-Adviser”), seeks to construct a portfolio of loans that it believes is less volatile than the general loan market. In addition, when making investments, the Sub-Adviser seeks to maintain appropriate liquidity and price transparency for the Portfolio. On an on-going basis, the Sub-Adviser adds or removes those individual loans that it believes will cause the Portfolio to outperform or underperform, respectively, the Primary and Secondary Indexes. When identifying prospective investment opportunities in Senior Loans, the Sub-Adviser currently intends to invest principally in Senior Loans that are below investment grade quality and will rely on fundamental credit analysis in an effort to attempt to minimize the loss of the Portfolio’s capital. While credit ratings assigned by Moody’s Investors Services, Inc., Standard & Poor’s, Inc. and/or Fitch Inc. (the “SROs” (statistical rating agencies)) will be considered, such ratings will not be determinative in the Sub-Adviser’s process in the selection of specific debt securities (including Senior Loans). The Senior Loans and other securities that the Sub-Adviser is likely to select for investment in by the Portfolio will typically be rated below investment grade quality by one or more of the SROs or, if unrated, will typically, in the opinion of the Sub-Adviser, be of similar credit quality. If circumstances cause the Sub-Adviser to take a negative credit view on an existing investment the Portfolio may, if the Sub-Adviser believes that circumstances require, exit the investment. The circumstances giving rise to the Sub-Adviser’s negative credit view may, but will not necessarily, coincide with a downgrade of the Senior Loan or other security’s credit rating. The Sub-Adviser expects to invest in Senior Loans, other loans and bonds of companies, including high yield securities, possessing the following attributes, which it believes will help generate higher risk adjusted total returns: Leading, defensible market positions.  The Sub-Adviser intends to invest in companies that it believes have developed strong positions within their respective markets and exhibit the potential to maintain sufficient cash flows and profitability to service their obligations in a range of economic environments. The Sub-Adviser will seek companies that it believes possess advantages in scale, scope, customer loyalty, product pricing, or product quality versus their competitors, thereby minimizing business risk and protecting profitability. Investing in companies with positive cash flow.  The Sub-Adviser intends to invest primarily in established companies which have demonstrated a record of profitability and cash flows over several economic cycles. The Sub-Adviser believes such companies are well-positioned to maintain consistent cash flow to service and repay their obligations and maintain growth in their businesses or market share. The Sub-Adviser does not intend to invest in primarily start-up companies, companies in turnaround situations or companies with speculative business plans. Proven management teams.  The Sub-Adviser intends to focus on investments in which the target company has an experienced management team with an established track record of success. The Sub-Adviser will typically require companies to have in place proper incentives to align management’s goals with the Portfolio’s goals. Private equity sponsorship.  Often the Sub-Adviser will seek to participate in transactions sponsored by what it believes to be high-quality private equity firms. The Sub-Adviser believes that a private equity sponsor’s willingness to invest significant sums of equity capital into a company is an implicit endorsement of the quality of the investment. Further, private equity sponsors of companies with significant investments at risk have the ability and a strong incentive to contribute additional capital in difficult economic times should operational issues arise. Diversification, concentration and reliance on other lenders.  The Sub-Adviser will seek to invest broadly among companies and industries, thereby potentially reducing the risk of a downturn in any one company or industry having a disproportionate impact on the value of the Portfolio’s portfolio. While the Portfolio does not treat banks originating loans as the issuers of such loans, it is possible that under a different interpretation the Portfolio may be deemed to concentrate its investments in the financial services industries. Loans, and the collateral securing them, are typically monitored by agents for the lenders, which may be the originating bank or banks. The Portfolio may be affected by the creditworthiness of the agent bank and other intermediate participants in a Senior Loan, in addition to the borrower, since rights that may exist under the loan against the borrower if the borrower defaults are typically asserted by or through the agent bank or intermediate participant. Agents are typically large commercial banks, although for Senior Loans that are not broadly syndicated they can also include thrift institutions, insurance companies or finance companies (or their affiliates). Such companies may be especially susceptible to the effects of changes in interest rates resulting from changes in U.S. or foreign fiscal or monetary policies, governmental regulations affecting capital raising activities or other economic or market fluctuations.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. SENIOR LOAN RISK:  Investments in Senior Loans are subject to credit risk and general investment risk. Credit risk refers to the possibility that the borrower of a Senior Loan will be unable and/or unwilling to make timely interest payments and/or repay the principal on its obligation. Default in the payment of interest or principal on a Senior Loan will result in a reduction in the value of the Senior Loan and consequently a reduction in the value of the Portfolio’s investments and a potential decrease in the net asset value (“NAV”) of the Portfolio. Senior Loans are also subject to the risk that the value of the collateral securing a Senior Loan may decline, be insufficient to meet the obligations of the borrower or be difficult to liquidate. In addition, the Portfolio’s access to the collateral may be limited by bankruptcy or other insolvency laws. Some Senior Loans are subject to the risk that a court, pursuant to fraudulent conveyance or other similar laws, could subordinate the Senior Loans to presently existing or future indebtedness of the borrower or take other action detrimental to lenders, including the Portfolio, such as invalidation of Senior Loans or causing interest previously paid to be refunded to the borrower. Senior Loans are also subject to high yield securities risks and liquidity risks described below. HIGH YIELD SECURITIES RISK:  The securities (including bank loans) in which the Portfolio primarily invests will typically be rated below investment grade. Securities rated below investment grade, commonly referred to as “junk bonds” or “high yield” securities, include securities that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Sub-Adviser, and may involve greater risks than securities in higher rating categories. Such securities are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” or “high yield” securities may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities or could result in lower prices than those used in calculating the Portfolio’s net asset value. Because of the substantial risks associated with investments in lower grade securities, investors could lose money on their investment in Shares of the Fund, both in the short-term and the long-term. LIQUIDITY RISK:  There is no organized exchange on which loans are traded and reliable market quotations may not be readily available. A majority of the Portfolio’s assets are likely to be invested in loans that are less liquid than securities traded on national exchanges. Loans with reduced liquidity involve greater risk than securities with more liquid markets. Available market quotations for such loans may vary over time, and if the credit quality of a loan unexpectedly declines, secondary trading of that loan may decline for a period of time. During periods of infrequent trading, valuing a loan can be more difficult and buying and selling a loan at an acceptable price can be more difficult and delayed. In the event that the Portfolio voluntarily or involuntarily liquidates portfolio assets during periods of infrequent trading, it may not receive full value for those assets. Therefore, elements of judgment may play a greater role in valuation of loans. To the extent that a secondary market exists for certain loans, the market may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods. FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR Blackstone / GSO Senior Loan ETF | SPDR Blackstone / GSO Senior Loan ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets	0.90%	[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets	none	[1]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets	0.90%	[1]
YEAR 1	rr_ExpenseExampleYear01	$ 92
YEAR 3	rr_ExpenseExampleYear03	$ 287

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

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SPDR SSgA Income Allocation ETF

SPDR^® SSgA Income Allocation ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Income Allocation ETF (the “Fund”) seeks to provide total return by focusing on investments in income and yield-generating assets.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Income Allocation ETF
MANAGEMENT FEES	[1][2]	0.70%
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1]	none
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]	0.70%

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3	YEAR 5	YEAR 10
SPDR SSgA Income Allocation ETF	72	224	390	871

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate (based on the Portfolio’s turnover rate) was 80% of the average value of its portfolio.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Income Allocation Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide exposure to four primary asset classes: (i) domestic and international equity securities; (ii) domestic and international investment grade and high yield debt securities; (iii) hybrid equity/debt securities (such as preferred stock and convertible securities); and (iv) real estate investment trusts (“REITs”). The Portfolio’s allocation among those asset classes will be in proportions consistent with the Adviser’s evaluation of the expected returns and
risks of each asset class as well as the allocation that, in the Adviser’s view, will best meet the Portfolio’s investment objective. The allocations to each asset class will change over time as the Adviser’s expectations of each asset class shift. The Portfolio’s indirect holdings by virtue of investing in ETPs representing these asset classes will consist of a diversified mix of domestic and international equity securities, investment grade and high yield government and corporate bonds, hybrid securities such as preferred stock and convertible securities, inflation protected securities, Build America Bonds, and REITs.

ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); and exchange traded notes (“ETNs”). The Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs:

EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income.

FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative.

HIGH YIELD SECURITIES RISK:  Securities rated below investment grade, commonly referred to as “junk bonds,” include bonds that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Adviser, and may involve greater risks than securities in higher rating categories. Such bonds are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities without taking a discount, which could be significant. High yield securities also may present greater credit risk because such securities may be issued in connection with corporate restructuring by highly leveraged issuers or may not be current in the payment of interest or principal or in default.

BUILD AMERICA BONDS RISK:  The market for Build America Bonds is smaller and less diverse than the broader municipal securities market. Because Congress did not extend the Build America Bond program, the ability of municipalities to issue Build America Bonds expired on December 31, 2010. As a result, the number of available Build America Bonds is limited, which may negatively affect the value of the Build America Bonds. In addition, certain aspects of the program may be subject to additional Federal or state level guidance or subsequent legislation. It is not known what additional restrictions, limitations or procedures may be implemented or what possible effect they will have on the market for Build America Bonds. There can be no assurance that Build America Bonds will be actively traded. The Build America Bonds outstanding as of December 31, 2010 will continue to be eligible for the federal interest rate subsidy, which continues for the life of the Build America Bonds; however, no bonds issued following expiration of the Build America Bond program will be eligible for the federal tax subsidy.

CONVERTIBLE SECURITIES RISK:  Convertible securities are bonds, debentures, notes, preferred stocks or other securities that may be converted or exchanged (by the holder or by the issuer) into shares of the underlying common stock (or cash or securities of equivalent value) at a stated exchange ratio. Convertible securities tend to be subordinate to other debt securities issued by the same issuer so such securities may not receive full repayment in the event of an issuer default. Also, issuers of convertible securities are often not as strong financially as issuers with higher credit ratings. Convertible securities generally provide yields higher than the underlying stocks, but generally lower than comparable non-convertible securities. Because of this higher yield, convertible securities generally sell at a price above their “conversion value,” which is the current market value of the stock to be received upon conversion. The difference between this conversion value and the price of convertible securities will vary over time depending on changes in the value of the underlying common stocks and interest rates.

PREFERRED SECURITIES RISK:  Generally, preferred security holders (such as the Portfolio) have no voting rights with respect to the issuing company unless certain events occur. In addition, preferred securities are subordinated to bonds and other debt instruments in a company’s capital structure and therefore will be subject to greater credit risk than those debt instruments. Unlike debt securities, dividend payments on a preferred security typically must be declared by the issuer’s board of directors. An issuer’s board of directors is generally not under any obligation to pay a dividend (even if such dividends have accrued), and may suspend payment of dividends on preferred securities at any time. In the event an issuer of preferred securities experiences economic difficulties, the issuer’s preferred securities may lose substantial value due to the reduced likelihood that the issuer’s board of directors will declare a dividend and the fact that the preferred security may be subordinated to other securities of the same issuer. There is a chance that the issuer of any of the Portfolio’s holdings will default (fail to make scheduled dividend payments on the preferred security or scheduled interest payments on other obligations of the issuer not held by the Portfolio).

REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act.

MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

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Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Income Allocation ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR® SSgA Income Allocation ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Income Allocation ETF (the “Fund”) seeks to provide total return by focusing on investments in income and yield-generating assets.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate (based on the Portfolio’s turnover rate) was 80% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	80.00%
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Income Allocation Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide exposure to four primary asset classes: (i) domestic and international equity securities; (ii) domestic and international investment grade and high yield debt securities; (iii) hybrid equity/debt securities (such as preferred stock and convertible securities); and (iv) real estate investment trusts (“REITs”). The Portfolio’s allocation among those asset classes will be in proportions consistent with the Adviser’s evaluation of the expected returns and risks of each asset class as well as the allocation that, in the Adviser’s view, will best meet the Portfolio’s investment objective. The allocations to each asset class will change over time as the Adviser’s expectations of each asset class shift. The Portfolio’s indirect holdings by virtue of investing in ETPs representing these asset classes will consist of a diversified mix of domestic and international equity securities, investment grade and high yield government and corporate bonds, hybrid securities such as preferred stock and convertible securities, inflation protected securities, Build America Bonds, and REITs. ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); and exchange traded notes (“ETNs”). The Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs: EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income. FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative. HIGH YIELD SECURITIES RISK:  Securities rated below investment grade, commonly referred to as “junk bonds,” include bonds that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Adviser, and may involve greater risks than securities in higher rating categories. Such bonds are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities without taking a discount, which could be significant. High yield securities also may present greater credit risk because such securities may be issued in connection with corporate restructuring by highly leveraged issuers or may not be current in the payment of interest or principal or in default. BUILD AMERICA BONDS RISK:  The market for Build America Bonds is smaller and less diverse than the broader municipal securities market. Because Congress did not extend the Build America Bond program, the ability of municipalities to issue Build America Bonds expired on December 31, 2010. As a result, the number of available Build America Bonds is limited, which may negatively affect the value of the Build America Bonds. In addition, certain aspects of the program may be subject to additional Federal or state level guidance or subsequent legislation. It is not known what additional restrictions, limitations or procedures may be implemented or what possible effect they will have on the market for Build America Bonds. There can be no assurance that Build America Bonds will be actively traded. The Build America Bonds outstanding as of December 31, 2010 will continue to be eligible for the federal interest rate subsidy, which continues for the life of the Build America Bonds; however, no bonds issued following expiration of the Build America Bond program will be eligible for the federal tax subsidy. CONVERTIBLE SECURITIES RISK:  Convertible securities are bonds, debentures, notes, preferred stocks or other securities that may be converted or exchanged (by the holder or by the issuer) into shares of the underlying common stock (or cash or securities of equivalent value) at a stated exchange ratio. Convertible securities tend to be subordinate to other debt securities issued by the same issuer so such securities may not receive full repayment in the event of an issuer default. Also, issuers of convertible securities are often not as strong financially as issuers with higher credit ratings. Convertible securities generally provide yields higher than the underlying stocks, but generally lower than comparable non-convertible securities. Because of this higher yield, convertible securities generally sell at a price above their “conversion value,” which is the current market value of the stock to be received upon conversion. The difference between this conversion value and the price of convertible securities will vary over time depending on changes in the value of the underlying common stocks and interest rates. PREFERRED SECURITIES RISK:  Generally, preferred security holders (such as the Portfolio) have no voting rights with respect to the issuing company unless certain events occur. In addition, preferred securities are subordinated to bonds and other debt instruments in a company’s capital structure and therefore will be subject to greater credit risk than those debt instruments. Unlike debt securities, dividend payments on a preferred security typically must be declared by the issuer’s board of directors. An issuer’s board of directors is generally not under any obligation to pay a dividend (even if such dividends have accrued), and may suspend payment of dividends on preferred securities at any time. In the event an issuer of preferred securities experiences economic difficulties, the issuer’s preferred securities may lose substantial value due to the reduced likelihood that the issuer’s board of directors will declare a dividend and the fact that the preferred security may be subordinated to other securities of the same issuer. There is a chance that the issuer of any of the Portfolio’s holdings will default (fail to make scheduled dividend payments on the preferred security or scheduled interest payments on other obligations of the issuer not held by the Portfolio). REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act. MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Income Allocation ETF | SPDR SSgA Income Allocation ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets	0.70%	[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets	none	[1]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets	0.70%	[1]
YEAR 1	rr_ExpenseExampleYear01	$ 72
YEAR 3	rr_ExpenseExampleYear03	224
YEAR 5	rr_ExpenseExampleYear05	390
YEAR 10	rr_ExpenseExampleYear10	$ 871

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Small Cap Risk Aware ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR SSgA Small Cap Risk Aware ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Small Cap Risk Aware ETF (the “Fund”) seeks to provide competitive returns compared to the small cap U.S. equity market and capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Small Cap Risk Aware Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. In seeking its objective, the Portfolio invests in a diversified selection of equity securities included in the Russell 2000 Index that SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) believes are aligned with predicted investor risk preferences. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in securities of small-cap companies. The Portfolio considers small-cap companies to be companies with market capitalizations falling within the range of the Russell 2000 Index at the time of initial purchase. In selecting securities for the Portfolio, the Adviser utilizes a proprietary quantitative investment process to measure and predict investor risk preferences. This process reflects the multidimensional and time-varying nature of risk, as stock characteristics the market deems to be safe or risky change over time. As a result, different periods of predicted uncertainty may result in portfolios that are more defensive or risk-seeking, depending on what the market considers safe and/or risky at each juncture (in light of factors such as beta, size, credit risk, credit spreads, exposure to gold, U.S. dollar exchange rates, and implied volatility). During periods of anticipated high risk, the Adviser will adjust the Portfolio’s composition to be defensive and may increase exposure to value companies. During periods of anticipated low risk, the Adviser will adjust the Portfolio’s composition to be risk-seeking and may increase exposure to growth companies. In periods of anticipated moderate risk, the Portfolio’s composition will more closely reflect the weighted composition of the Russell 2000 Index. Due to on-going market fluctuations, the Adviser believes the resulting ebbing and flowing of risk preferences give this strategy the potential to provide competitive returns relative to the Russell 2000 Index over the long term. The Portfolio is non-diversified for purposes of the Investment Company Act of 1940, and as a result may invest a greater percentage of its assets in a particular issuer than a diversified fund. However, the Portfolio expects to have exposure to a diversified mix of equity securities.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general. FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market. SMALL CAP RISK: Small-sized companies may be more volatile and more likely than large- and mid-capitalization companies to have relatively limited product lines, markets or financial resources, or depend on a few key employees. Returns on investments in stocks of small companies could trail the returns on investments in stocks of larger companies. GROWTH RISK: The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on “growth” securities may or may not move in tandem with the returns on other styles of investing or the overall stock market. VALUE RISK: A “value” style of investing emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Small Cap Risk Aware ETF | SPDR SSgA Small Cap Risk Aware ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Large Cap Risk Aware ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR SSgA Large Cap Risk Aware ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Large Cap Risk Aware ETF (the “Fund”) seeks to provide competitive returns compared to the large cap U.S. equity market and capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Large Cap Risk Aware Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. In seeking its objective, the Portfolio invests in a diversified selection of equity securities included in the Russell 1000 Index that SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) believes are aligned with predicted investor risk preferences. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in securities of large-cap companies. The Portfolio considers large-cap companies to be companies with market capitalizations falling within the range of the Russell 1000 Index at the time of initial purchase. In selecting securities for the Portfolio, the Adviser utilizes a proprietary quantitative investment process to measure and predict investor risk preferences. This process reflects the multidimensional and time-varying nature of risk, as stock characteristics the market deems to be safe or risky change over time. As a result, different periods of predicted uncertainty may result in portfolios that are more defensive or risk-seeking, depending on what the market considers safe and/or risky at each juncture (in light of factors such as beta, size, credit risk, credit spreads, exposure to gold, U.S. dollar exchange rates, and implied volatility). During periods of anticipated high risk, the Adviser will adjust the Portfolio’s composition to be defensive and may increase exposure to value companies. During periods of anticipated low risk, the Adviser will adjust the Portfolio’s composition to be risk-seeking and may increase exposure to growth companies. In periods of anticipated moderate risk, the Portfolio’s composition will more closely reflect the weighted composition of the Russell 1000 Index. Due to on-going market fluctuations, the Adviser believes the resulting ebbing and flowing of risk preferences give this strategy the potential to provide competitive returns relative to the Russell 1000 Index over the long term. The Portfolio is non-diversified for purposes of the Investment Company Act of 1940, and as a result may invest a greater percentage of its assets in a particular issuer than a diversified fund. However, the Portfolio expects to have exposure to a diversified mix of equity securities.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general. FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market. LARGE CAP RISK: Returns on investments in stocks of large companies could trail the returns on investments in stocks of smaller and mid-sized companies. GROWTH RISK: The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on “growth” securities may or may not move in tandem with the returns on other styles of investing or the overall stock market. VALUE RISK: A “value” style of investing emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Large Cap Risk Aware ETF | SPDR SSgA Large Cap Risk Aware ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
Document Creation Date	dei_DocumentCreationDate	Oct. 28, 2013

XML

SPDR SSgA US Minimum Volatility ETF

SPDR SSgA US Minimum Volatility ETF

INVESTMENT OBJECTIVE

The SPDR SSgA US Minimum Volatility ETF (the “Fund”) seeks to provide competitive long-term returns while maintaining low long-term volatility relative to the broad U.S. market.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA US Minimum Volatility ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA US Minimum Volatility ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA US Minimum Volatility Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) utilizes a proprietary quantitative investment process to select a portfolio of equity securities that the Adviser believes will exhibit low long-term volatility and provide competitive long-term returns relative to the broad U.S. market. Volatility is a statistical measurement of the magnitude of up and down fluctuations in the value of a financial instrument or index over time. Volatility may result in rapid and dramatic price swings. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in U.S. investments. The Adviser expects to favor securities with low exposure to market risk factors and low security-specific risk. The Adviser considers market risk factors to include, among others, a security’s size, momentum, value, liquidity, leverage and growth. While the Adviser attempts to manage the Fund’s volatility exposure to stabilize performance, there can be no guarantee that the Fund will reach its target volatility. Additionally, the Adviser implements certain risk constraints at the security, industry, size exposure, and sector levels. Through this quantitative process of security selection and portfolio diversification, the Adviser expects that the portfolio will be subject to a low level of absolute risk (as defined by standard deviation of returns) and thus should exhibit low volatility over the long term.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio’s and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Conservative Ultra Short Bond ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR SSgA Conservative Ultra Short Term Bond ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Conservative Ultra Short Term Bond ETF (the “Fund”) seeks to provide current income consistent with preservation of capital and daily liquidity through short duration high quality investments with the avoidance of excessive portfolio volatility.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Conservative Ultra Short Term Bond Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests, under normal circumstances, at least 80% of the Portfolio’s net assets (plus the amount of borrowings for investment purposes) in a diversified portfolio of U.S. dollar-denominated investment grade fixed income securities. The Portfolio primarily invests in investment grade fixed income securities that are rated a minimum of A- or higher by Standard & Poor’s Financial Services LLC and/or Fitch Inc., or A3 or higher by Moody’s Investors Service, Inc., or, if unrated, determined by the management team to be of equivalent quality. The Portfolio invests in fixed and floating rate securities of varying maturities, such as corporate obligations (including commercial paper of U.S. and foreign entities, master notes, and medium term notes); government bonds (including U.S. Treasury Bills, notes, and bonds); agency securities; privately-issued securities; asset-backed and mortgage-backed securities; money market instruments (including U.S. and foreign bank time deposits, certificates of deposit, and banker acceptances) and other investment companies. The Portfolio may also invest in exchange traded products (“ETPs”). ETPs include exchange traded funds registered under the Investment Company Act of 1940, as amended, (the “1940 Act”) that seek to track the performance of a market index (“Underlying ETFs”) and exchange traded notes. In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services. Under normal circumstances, the effective duration of the Portfolio is expected to be four months or less. Effective duration is a measure of the Portfolio’s price sensitivity to changes in yields or interest rates; however, investors should be aware that effective duration is not an exact measurement and may not reliably predict a particular security’s price sensitivity to changes in yield or interest rates. In addition, the Portfolio expects to maintain a weighted average maturity between six and eighteen months. Weighted average maturity is a U.S. dollar-weighted average of the remaining term to maturity of the underlying securities in the Portfolio. For the purposes of determining the Portfolio’s weighted average maturity, a security’s final maturity date, or for amortizing securities such as asset-backed and mortgage-backed securities, its weighted average life will be used for calculation purposes. The Portfolio and Fund are not money market funds and do not seek to maintain a stable net asset value of $1.00 per share.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. DEBT SECURITIES INVESTING RISK: The value of debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income. FLOATING RATE NOTES INVESTING RISK: Floating rate notes protect investors against a rise in interest rates, but also carry lower yields than fixed notes of the same maturity. The interest rate for a floating rate note resets or adjusts periodically (normally on a daily, monthly, quarterly or semiannual basis by reference to a base lending rate (such as LIBOR). Because rates on floating rate notes reset only periodically, changes in prevailing interest rates (particularly sudden and significant changes) can be expected to cause fluctuations in net asset value. Floating rate notes generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Portfolio needs to liquidate such loans. U.S. TREASURY OBLIGATIONS RISK: Treasury obligations may differ from other fixed income securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the United States may cause the value of its Treasury obligations to decline. U.S. GOVERNMENT AGENCY SECURITIES RISK: Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, performance will be adversely impacted. SOVEREIGN OBLIGATIONS RISK: The Portfolio invests in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations. ASSET-BACKED AND MORTGAGE-BACKED SECURITIES RISK: Asset-backed and mortgage-backed securities (residential and commercial) represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. These securities, in most cases, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. These securities are subject to the risk of default on the underlying asset or mortgage, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities. PREPAYMENT RISK: Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income. PRIVATELY-ISSUED SECURITIES RISK. The Portfolio will invest in privately-issued securities, including those which are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act of 1933, as amended (the “1933 Act”). Privately-issued securities are securities that have not been registered under the 1933 Act and as a result are subject to legal restrictions on resale. Privately-issued securities are not traded on established markets and may be illiquid, difficult to value and subject to wide fluctuations in value. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Portfolio from disposing of them promptly at reasonable prices. DERIVATIVES RISK: A derivative is a financial contract the value of which depends on, or is derived from, the value of a financial asset (such as stock, bond or currency), a physical asset (such as gold) or a market index (such as the S&P 500 Index). The Fund may invest in forward foreign currency contracts. Forward foreign currency contracts involve an obligation to purchase or sell a specific amount of currency at a future date or date range at a specific price, thereby fixing the exchange rate for a specified time in the future. When used for hedging purposes, forward foreign currency contracts tend to limit any potential gain that may be realized if the value of the Fund’s foreign holdings increases because of currency fluctuations. Compared to conventional securities, derivatives can be more sensitive to changes in interest rates or to sudden fluctuations in market prices and thus the Fund’s losses may be greater if it invests in derivatives than if it invests only in conventional securities. FOREIGN INVESTMENT RISK: Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. FINANCIAL SECTOR RISK: Financial services companies are subject to extensive governmental regulation which may limit both the amounts and types of loans and other financial commitments they can make, and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change or due to increased competition. In addition, the recent deterioration of the credit markets generally has caused an adverse impact in a broad range of markets, including U.S. and international credit and interbank money markets generally, thereby affecting a wide range of financial institutions and markets. Recent events in the financial sector have resulted, and may continue to result, in an unusually high degree of volatility in the financial markets, both domestic and foreign, and cause certain financial services companies to incur large losses. Numerous financial services companies have experienced substantial declines in the valuations of their assets, taken action to raise capital (such as the issuance of debt or equity securities), or even ceased operations. These actions have caused the securities of many financial services companies to experience a dramatic decline in value. Credit losses resulting from financial difficulties of borrowers and financial losses associated with investment activities can negatively impact the sector. Insurance companies may be subject to severe price competition. EXCHANGE TRADED PRODUCTS RISK: The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an exchange traded note (“ETN”) may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs: AFFILIATED ETP RISK: The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. NON-DIVERSIFICATION RISK: The Fund is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio’s and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	NON-DIVERSIFICATION RISK: The Fund is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Conservative Ultra Short Bond ETF | SPDR SSgA Conservative Ultra Short Bond ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR SSgA Global Allocation ETF

SPDR^® SSgA Global Allocation ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Global Allocation ETF (the “Fund”) seeks to provide capital appreciation.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Global Allocation ETF
MANAGEMENT FEES	[1][2]	0.35%
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1]	none
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]	0.35%

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3	YEAR 5	YEAR 10
SPDR SSgA Global Allocation ETF	36	113	197	443

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate (based on the Portfolio’s turnover rate) was 123% of the average value of its portfolio.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Global Allocation Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide balanced exposure to domestic and international debt and equity securities. The Portfolio typically allocates approximately 60% of its assets to equity securities, though this percentage can vary based on the Adviser’s tactical decisions. The allocations to each asset class will change over time as the Adviser’s expectations of each asset class shift. The Portfolio’s indirect holdings by virtue of investing in ETPs representing these asset classes consist of a diversified mix of domestic and international, including emerging market, equity securities across all market capitalizations, investment grade and high yield government and corporate bonds, inflation protected securities, mortgage pass through securities, commercial mortgage backed securities, asset backed securities, commodities and real estate investment trusts (“REITs”). The Portfolio, through its investments in ETPs, will generally invest at least 30% of its assets in securities of issuers economically tied to countries other than the United States and will generally hold securities of issuers economically tied to at least three countries, including the United States. In determining if a security is economically tied to a non-U.S. country, the Portfolio generally looks to the country of incorporation of the issuer as listed on Bloomberg, a widely recognized provider of market information. However, the Adviser may determine a security is economically tied to a non-U.S. country based on other factors, such as an issuer’s country of domicile, where more than 50% of an issuer’s revenues are generated or where an issuer’s primary exchange is located. As a result, a security may be economically tied to more than one country.

ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); exchange traded commodity trusts; and exchange traded notes (“ETNs”). The Portfolio may invest in ETPs that are qualified publicly traded partnerships (“QPTPs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs:

EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income.

FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative.

COMMODITIES RISK:  Exposure to the commodities markets may subject the Portfolio to greater volatility than investments in traditional securities. Commodities are subject to substantial price fluctuations over short periods of time and may be affected by unpredictable economic, political and environmental events. Factors that may significantly affect the prices of commodities include, but are not limited to: global supply and demand; domestic and international interest rates and investors’ expectations of interest rates; inflation rates and investors’ expectations of inflation rates; the investment and trading activities of commodity futures contracts; political, economic, or financial events, both globally and regionally.

TAX RISK:  Regulated investment companies are subject to favorable tax treatment under the Internal Revenue Code. To qualify as a regulated investment company, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. Thus, income from the Portfolio’s investments in certain commodities-related investments may cause the Fund not to qualify as a regulated investment company. The Portfolio may invest up to 25% of its total assets in one or more ETPs that are QPTPs and whose principal activities are the buying and selling of commodities or options, futures, or forwards with respect to commodities. Income from QPTPs is generally qualifying income. If an ETP fails to qualify as a QPTP, the income generated from the Portfolio’s investment in the ETP may not be qualifying income. The Portfolio will only invest in such an ETP if it intends to qualify as a QPTP, but there is no guarantee that each such ETP will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of such ETPs as QPTPs. If the Fund fails to qualify as a regulated investment company, the Fund will be subject to tax, which will reduce returns to shareholders. Such a failure will also alter the treatment of distributions to shareholders.

HIGH YIELD SECURITIES RISK:  Securities rated below investment grade, commonly referred to as “junk bonds,” include bonds that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Adviser, and may involve greater risks than securities in higher rating categories. Such bonds are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities without taking a discount, which could be significant. High yield securities also may present greater credit risk because such securities may be issued in connection with corporate restructuring by highly leveraged issuers or may not be current in the payment of interest or principal or in default.

U.S. GOVERNMENT AGENCY SECURITIES RISK:  Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, the performance of the Portfolio and, therefore, the Fund will be adversely impacted.

PREPAYMENT RISK:  Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income.

MORTGAGE-BACKED SECURITIES RISK:  Mortgage-backed securities, other than Government National Mortgage Association (“GNMA”) mortgage-backed securities, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. Mortgage-backed securities tend to increase in value less than other debt securities when interest rates decline, but are subject to similar risk of decline in market value during periods of rising interest rates. Because of prepayment and extension risk, mortgage-backed securities react differently to changes in interest rates than other bonds. Small movements in interest rates (both increases and decreases) may quickly and significantly affect the value of certain mortgage-backed securities.

MORTGAGE PASS-THROUGH SECURITIES RISK:  Most transactions in mortgage pass-through securities occur through standardized contracts for future delivery in which the exact mortgage pools to be delivered are not specified until a few days prior to settlement, referred to as a “to-be-announced transaction” or “TBA Transaction.” In a TBA Transaction, the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount and price. Default by or bankruptcy of a counterparty to a TBA Transaction would expose the Portfolio to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA Transaction.

REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act.

MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Multi-Asset Real Return ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	FUND SUMMARIES SPDR® SSgA Multi-Asset Real Return ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Multi-Asset Real Return ETF (the “Fund”) seeks to achieve real return consisting of capital appreciation and current income.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate (based on the Portfolio’s turnover rate) was 31% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	31.00%
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Multi-Asset Real Return Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide exposure to four primary asset classes: (i) inflation protected securities issued by the United States government, its agencies and/or instrumentalities, as well as inflation protected securities issued by foreign governments, agencies, and/or instrumentalities; (ii) domestic and international real estate securities; (iii) commodities; and (iv) publicly-traded companies in natural resources and/or commodities businesses. The Portfolio’s allocation among those asset classes will be in proportions consistent with the Adviser’s evaluation of the expected returns and risks of each asset class as well as the allocation that, in the Adviser’s view, will best meet the Portfolio’s investment objective. The allocations to each asset class will change over time as the Adviser’s expectations of each asset class shift. The Portfolio’s indirect holdings by virtue of investing in ETPs representing those asset classes will consist of a diversified mix of domestic and international equity securities, government bonds, inflation protected securities, commodities and real estate investment trusts (“REITs”). The Adviser considers real return to be a rate of return above the rate of inflation over a market cycle. ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); exchange traded commodity trusts; and exchange traded notes (“ETNs”). The Portfolio may invest in ETPs that are qualified publicly traded partnerships (“QPTPs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs: EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. INFLATION PROTECTED SECURITIES RISK:  Inflation protected securities, such as TIPS, generally fluctuate in response to changes in “real” interest rates. Real interest rates represent nominal (stated) interest rates reduced by the expected impact of inflation. Generally, an inflation protected security’s value will decrease when real interest rates rise and increase when real interest rates fall. Interest payments on inflation-protected debt securities can be unpredictable and will vary as the principal and/or interest is adjusted for inflation. During periods of “deflation,” the principal and income of an inflation protected security may decline in price, which could result in losses for the Fund. DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income. FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative. COMMODITIES RISK:  Exposure to the commodities markets may subject the Portfolio to greater volatility than investments in traditional securities. Commodities are subject to substantial price fluctuations over short periods of time and may be affected by unpredictable economic, political and environmental events. Factors that may significantly affect the prices of commodities include, but are not limited to: global supply and demand; domestic and international interest rates and investors’ expectations of interest rates; inflation rates and investors’ expectations of inflation rates; the investment and trading activities of commodity futures contracts; political, economic, or financial events, both globally and regionally. TAX RISK:  Regulated investment companies are subject to favorable tax treatment under the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”). To qualify as a regulated investment company, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. Thus, income from the Portfolio’s investments in certain commodities-related investments may cause the Fund not to qualify as a regulated investment company. The Portfolio may invest up to 25% of its total assets in one or more ETPs that are QPTPs and whose principal activities are the buying and selling of commodities or options, futures, or forwards with respect to commodities. Income from QPTPs is generally qualifying income. If an ETP fails to qualify as a QPTP, the income generated from the Portfolio’s investment in the ETP may not be qualifying income. The Portfolio will only invest in such an ETP if it intends to qualify as a QPTP, but there is no guarantee that each such ETP will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of such ETPs as QPTPs. If the Fund fails to qualify as a regulated investment company, the Fund will be subject to tax, which will reduce returns to shareholders. Such a failure will also alter the treatment of distributions to shareholders. AGRICULTURE SECTOR RISK:  Economic forces, including forces affecting agricultural markets, as well as government policies and regulations affecting the agricultural sector and related industries, could adversely related investments. Agricultural and livestock production and trade flows are significantly affected by government policies and regulations. Governmental policies affecting the agricultural sector, such as taxes, tariffs, duties, subsidies and import and export restrictions on agricultural commodities, commodity products and livestock, can influence industry profitability, the planting/raising of certain crops/livestock versus other uses of resources, the location and size of crop and livestock production, whether unprocessed or processed commodity products are traded and the volume and types of imports and exports. In addition, the companies in the agriculture sector must comply with a broad range of environmental laws and regulations. Additional or more stringent environmental laws and regulations may be enacted in the future and such changes could have a material adverse effect on the business of such companies. In addition, agricultural and livestock businesses may be significantly affected by adverse weather, pollution and/or disease which could limit or halt production. ENERGY SECTOR RISK:  Energy companies typically develop and produce crude oil and natural gas and provide drilling and other energy resources production and distribution related services. Stock prices for these types of companies are affected by supply and demand both for their specific product or service and for energy products in general. The price of oil and gas, exploration and production spending, government regulation, world events, exchange rates and economic conditions will likewise affect the performance of these companies. Correspondingly, securities of companies in the energy field are subject to swift price and supply fluctuations caused by events relating to international politics, energy conservation, the success of exploration projects, and tax and other governmental regulatory policies. Weak demand for the companies’ products or services or for energy products and services in general, as well as negative developments in these other areas, would adversely impact performance of energy sector companies. Oil and gas exploration and production can be significantly affected by natural disasters as well as changes in exchange rates, interest rates, government regulation, world events and economic conditions. These companies may be at risk for environmental damage claims. METALS AND MINING SECTOR RISK:  The metals and mining sector can be significantly affected by events relating to international political and economic developments, energy conservation, resource availability, the success of exploration projects, commodity prices, and tax and other government regulations. Investments in metals and mining industry companies may be speculative and may be subject to greater price volatility than investments in other types of companies. Risks of metals and mining investments include: changes in international monetary policies or economic and political conditions that can affect the supply of precious metals and consequently the value of metals and mining company investments; the United States or foreign governments may pass laws or regulations limiting metals investments for strategic or other policy reasons; and increased environmental or labor costs may depress the value of metals and mining investments. REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act. MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Multi-Asset Real Return ETF | SPDR SSgA Multi-Asset Real Return ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets	0.70%	[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets	none	[1]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets	0.70%	[1]
YEAR 1	rr_ExpenseExampleYear01	$ 72
YEAR 3	rr_ExpenseExampleYear03	224
YEAR 5	rr_ExpenseExampleYear05	390
YEAR 10	rr_ExpenseExampleYear10	$ 871

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

XML

SPDR MFS Systematic Core Equity ETF

SPDR MFS Systematic Core Equity ETF

INVESTMENT OBJECTIVE

The SPDR MFS Systematic Core Equity ETF’s (the “Fund”) investment objective is to seek capital appreciation.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR MFS Systematic Core Equity ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR MFS Systematic Core Equity ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA MFS Systematic Core Equity Portfolio (the "Portfolio"), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in equity securities. Equity securities in which the Portfolio invests include common stocks, preferred stocks and securities convertible into stocks.

In selecting securities for the Portfolio, Massachusetts Financial Services Company (the "Sub-Adviser" or "MFS") utilizes a bottom-up approach to buying and selling investments for the Portfolio. Investments are selected based on fundamental and quantitative analysis. MFS uses fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions to identify potential investments. Factors considered may include analysis of an issuer's earnings, cash flows, competitive position, and management ability. MFS then uses quantitative models that systematically evaluate an issuer's valuation, price and earnings momentum, earnings quality, and other factors to determine which investments to buy and sell.

While the Sub-Adviser may invest the Portfolio's assets in companies of any size, the Sub-Adviser generally focuses on companies with large market capitalizations. In selecting investments for the Portfolio, the Sub-Adviser is not constrained to any particular investment style. The Sub-Adviser may invest the Portfolio's assets in the stocks of companies it believes have above average earnings growth potential compared to other companies (growth companies), in the stocks of companies it believes are undervalued compared to their perceived worth (value companies), or in a combination of growth and value companies.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

PREFERRED SECURITIES RISK: Generally, preferred security holders (such as the Portfolio) have no voting rights with respect to the issuing company unless certain events occur. In addition, preferred securities are subordinated to bonds and other debt instruments in a company’s capital structure and therefore will be subject to greater credit risk than those debt instruments. Unlike debt securities, dividend payments on a preferred security typically must be declared by the issuer’s board of directors. An issuer’s board of directors is generally not under any obligation to pay a dividend (even if such dividends have accrued), and may suspend payment of dividends on preferred securities at any time. In the event an issuer of preferred securities experiences economic difficulties, the issuer’s preferred securities may lose substantial value due to the reduced likelihood that the issuer’s board of directors will declare a dividend and the fact that the preferred security may be subordinated to other securities of the same issuer. There is a chance that the issuer of any of the Portfolio’s holdings will default (fail to make scheduled dividend payments on the preferred security or scheduled interest payments on other obligations of the issuer not held by the Portfolio).

CONVERTIBLE SECURITIES RISK: Convertible securities are bonds, debentures, notes, preferred stocks or other securities that may be converted or exchanged (by the holder or by the issuer) into shares of the underlying common stock (or cash or securities of equivalent value) at a stated exchange ratio. Convertible securities tend to be subordinate to other debt securities issued by the same issuer so such securities may not receive full repayment in the event of an issuer default. Also, issuers of convertible securities are often not as strong financially as issuers with higher credit ratings. Convertible securities generally provide yields higher than the underlying stocks, but generally lower than comparable non-convertible securities. Because of this higher yield, convertible securities generally sell at a price above their “conversion value,” which is the current market value of the stock to be received upon conversion. The difference between this conversion value and the price of convertible securities will vary over time depending on changes in the value of the underlying common stocks and interest rates.

COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general.

GROWTH RISK: The Portfolio may emphasize a “growth” style of investing. The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on “growth” securities may or may not move in tandem with the returns on other styles of investing or the overall stock market.

VALUE RISK: The Portfolio may employ a “value” style of investing that emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market.

LARGE CAP RISK: Returns on investments in stocks of large U.S. companies could trail the returns on investments in stocks of smaller and mid-sized companies.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Sub-Adviser’s investment strategy may not produce the intended results and may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

SPDR SSgA Multi-Asset Real Return ETF

FUND SUMMARIES

SPDR^® SSgA Multi-Asset Real Return ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Multi-Asset Real Return ETF (the “Fund”) seeks to achieve real return consisting of capital appreciation and current income.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Multi-Asset Real Return ETF
MANAGEMENT FEES	[1][2]	0.70%
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1]	none
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]	0.70%

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3	YEAR 5	YEAR 10
SPDR SSgA Multi-Asset Real Return ETF	72	224	390	871

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate (based on the Portfolio’s turnover rate) was 31% of the average value of its portfolio.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Multi-Asset Real Return Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide exposure to four primary asset classes: (i) inflation protected securities issued by the United States government, its agencies and/or instrumentalities, as well as inflation protected securities issued by foreign governments, agencies, and/or instrumentalities; (ii) domestic and international real estate securities; (iii) commodities; and (iv) publicly-traded companies in natural resources and/or commodities businesses. The Portfolio’s allocation among those asset classes will be in proportions consistent with the Adviser’s evaluation of the expected returns and risks of each asset class as well as the allocation that, in the Adviser’s view, will best meet the Portfolio’s investment objective. The allocations to each asset class will change over time as the Adviser’s expectations of each asset class shift. The Portfolio’s indirect holdings by virtue of investing in ETPs representing those asset classes will consist of a diversified mix of domestic and international equity securities, government bonds, inflation protected securities, commodities and real estate investment trusts (“REITs”). The Adviser considers real return to be a rate of return above the rate of inflation over a market cycle.

ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); exchange traded commodity trusts; and exchange traded notes (“ETNs”). The Portfolio may invest in ETPs that are qualified publicly traded partnerships (“QPTPs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs:

EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

INFLATION PROTECTED SECURITIES RISK:  Inflation protected securities, such as TIPS, generally fluctuate in response to changes in “real” interest rates. Real interest rates represent nominal (stated) interest rates reduced by the expected impact of inflation. Generally, an inflation protected security’s value will decrease when real interest rates rise and increase when real interest rates fall. Interest payments on inflation-protected debt securities can be unpredictable and will vary as the principal and/or interest is adjusted for inflation. During periods of “deflation,” the principal and income of an inflation protected security may decline in price, which could result in losses for the Fund.

DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income.

FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative.

COMMODITIES RISK:  Exposure to the commodities markets may subject the Portfolio to greater volatility than investments in traditional securities. Commodities are subject to substantial price fluctuations over short periods of time and may be affected by unpredictable economic, political and environmental events. Factors that may significantly affect the prices of commodities include, but are not limited to: global supply and demand; domestic and international interest rates and investors’ expectations of interest rates; inflation rates and investors’ expectations of inflation rates; the investment and trading activities of commodity futures contracts; political, economic, or financial events, both globally and regionally.

TAX RISK:  Regulated investment companies are subject to favorable tax treatment under the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”). To qualify as a regulated investment company, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. Thus, income from the Portfolio’s investments in certain commodities-related investments may cause the Fund not to qualify as a regulated investment company. The Portfolio may invest up to 25% of its total assets in one or more ETPs that are QPTPs and whose principal activities are the buying and selling of commodities or options, futures, or forwards with respect to commodities. Income from QPTPs is generally qualifying income. If an ETP fails to qualify as a QPTP, the income generated from the Portfolio’s investment in the ETP may not be qualifying income. The Portfolio will only invest in such an ETP if it intends to qualify as a QPTP, but there is no guarantee that each such ETP will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of such ETPs as QPTPs. If the Fund fails to qualify as a regulated investment company, the Fund will be subject to tax, which will reduce returns to shareholders. Such a failure will also alter the treatment of distributions to shareholders.

AGRICULTURE SECTOR RISK:  Economic forces, including forces affecting agricultural markets, as well as government policies and regulations affecting the agricultural sector and related industries, could adversely related investments. Agricultural and livestock production and trade flows are significantly affected by government policies and regulations. Governmental policies affecting the agricultural sector, such as taxes, tariffs, duties, subsidies and import and export restrictions on agricultural commodities, commodity products and livestock, can influence industry profitability, the planting/raising of certain crops/livestock versus other uses of resources, the location and size of crop and livestock production, whether unprocessed or processed commodity products are traded and the volume and types of imports and exports. In addition, the companies in the agriculture sector must comply with a broad range of environmental laws and regulations. Additional or more stringent environmental laws and regulations may be enacted in the future and such changes could have a material adverse effect on the business of such companies. In addition, agricultural and livestock businesses may be significantly affected by adverse weather, pollution and/or disease which could limit or halt production.

ENERGY SECTOR RISK:  Energy companies typically develop and produce crude oil and natural gas and provide drilling and other energy resources production and distribution related services. Stock prices for these types of companies are affected by supply and demand both for their specific product or service and for energy products in general. The price of oil and gas, exploration and production spending, government regulation, world events, exchange rates and economic conditions will likewise affect the performance of these companies. Correspondingly, securities of companies in the energy field are subject to swift price and supply fluctuations caused by events relating to international politics, energy conservation, the success of exploration projects, and tax and other governmental regulatory policies. Weak demand for the companies’ products or services or for energy products and services in
general, as well as negative developments in these other areas, would adversely impact performance of energy sector companies. Oil and gas exploration and production can be significantly affected by natural disasters as well as changes in exchange rates, interest rates, government regulation, world events and economic conditions. These companies may be at risk for environmental damage claims.

METALS AND MINING SECTOR RISK:  The metals and mining sector can be significantly affected by events relating to international political and economic developments, energy conservation, resource availability, the success of exploration projects, commodity prices, and tax and other government regulations. Investments in metals and mining industry companies may be speculative and may be subject to greater price volatility than investments in other types of companies. Risks of metals and mining investments include: changes in international monetary policies or economic and political conditions that can affect the supply of precious metals and consequently the value of metals and mining company investments; the United States or foreign governments may pass laws or regulations limiting metals investments for strategic or other policy reasons; and increased environmental or labor costs may depress the value of metals and mining investments.

REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act.

MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Ultra Short Term Bond ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR® SSgA Ultra Short Term Bond ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Ultra Short Term Bond ETF (the “Fund”) seeks to provide current income consistent with preservation of capital and daily liquidity through short duration high quality investments.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Ultra Short Term Bond Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests, under normal circumstances, at least 80% of the Portfolio’s net assets (plus the amount of borrowings for investment purposes) in a diversified portfolio of U.S. dollar-denominated investment grade fixed income securities. The Portfolio primarily invests in investment grade fixed income securities that are rated at the time of purchase a minimum of A- or higher by Standard & Poor’s Financial Services LLC and/or Fitch Inc., or A3 or higher by Moody’s Investors Service, Inc., or, if unrated, determined by the management team to be of equivalent quality. The Portfolio invests in fixed and floating rate securities of varying maturities, such as corporate obligations (including commercial paper of U.S. and foreign entities, master notes, and medium term notes); government bonds (including U.S. Treasury Bills, notes, and bonds); agency securities; privately-issued securities; asset-backed and mortgage-backed securities; money market instruments (including U.S. and foreign bank time deposits, certificates of deposit, and banker acceptances) and other investment companies. The Portfolio may also invest in exchange traded products (“ETPs”). ETPs include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”) and exchange traded notes (“ETNs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services. Under normal circumstances, the effective duration of the Portfolio is expected to be between three and nine months. Effective duration is a measure of the Portfolio’s price sensitivity to changes in yields or interest rates; however, investors should be aware that effective duration is not an exact measurement and may not reliably predict a particular security’s price sensitivity to changes in yield or interest rates. In addition, the Portfolio expects to maintain a weighted average maturity between six and eighteen months. Weighted average maturity is a U.S. dollar-weighted average of the remaining term to maturity of the underlying securities in the Portfolio. For the purposes of determining the Portfolio’s weighted average maturity, a security’s final maturity date, or for amortizing securities such as asset-backed and mortgage-backed securities, its weighted average life will be used for calculation purposes. The Adviser buys and sells securities for the Portfolio based on its analysis of credit quality and overall portfolio duration. A security will generally be sold from the Portfolio where the Adviser believes that a different security, viewed in light of its maturity, provides a higher yield. The Portfolio and Fund are not money market funds and do not seek to maintain a stable net asset value of $1.00 per share.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. DEBT SECURITIES INVESTING RISK:  The value of debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income. FLOATING RATE NOTES INVESTING RISK:  Floating rate notes protect investors against a rise in interest rates, but also carry lower yields than fixed notes of the same maturity. The interest rate for a floating rate note resets or adjusts periodically (normally on a daily, monthly, quarterly or semiannual basis by reference to a base lending rate (such as LIBOR). Because rates on floating rate notes reset only periodically, changes in prevailing interest rates (particularly sudden and significant changes) can be expected to cause fluctuations in net asset value. Floating rate notes generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Portfolio needs to liquidate such loans. U.S. TREASURY OBLIGATIONS RISK:  Treasury obligations may differ from other fixed income securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the United States may cause the value of its Treasury obligations to decline. U.S. GOVERNMENT AGENCY SECURITIES RISK:  Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, performance will be adversely impacted. SOVEREIGN OBLIGATIONS RISK:  The Portfolio invests in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations. ASSET-BACKED AND MORTGAGE-BACKED SECURITIES RISK:  Asset-backed and mortgage-backed securities (residential and commercial) represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. These securities, in most cases, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. These securities are subject to the risk of default on the underlying asset or mortgage, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities. PREPAYMENT RISK:  Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income. PRIVATELY-ISSUED SECURITIES RISK:  The Portfolio will invest in privately-issued securities, including those which are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act. Privately-issued securities are securities that have not been registered under the Securities Act and as a result are subject to legal restrictions on resale. Privately-issued securities are not traded on established markets and may be illiquid, difficult to value and subject to wide fluctuations in value. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Portfolio from disposing of them promptly at reasonable prices. FOREIGN INVESTMENT RISK:  Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the U.S. pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; different practices for clearing and settling trades; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of the currency of the country in which the Fund has invested could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. FINANCIAL SECTOR RISK:  Financial services companies are subject to extensive governmental regulation which may limit both the amounts and types of loans and other financial commitments they can make, and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change or due to increased competition. In addition, the recent deterioration of the credit markets generally has caused an adverse impact in a broad range of markets, including U.S. and international credit and interbank money markets generally, thereby affecting a wide range of financial institutions and markets. Recent events in the financial sector have resulted, and may continue to result, in an unusually high degree of volatility in the financial markets, both domestic and foreign, and cause certain financial services companies to incur large losses. Numerous financial services companies have experienced substantial declines in the valuations of their assets, taken action to raise capital (such as the issuance of debt or equity securities), or even ceased operations. These actions have caused the securities of many financial services companies to experience a dramatic decline in value. Credit losses resulting from financial difficulties of borrowers and financial losses associated with investment activities can negatively impact the sector. Insurance companies may be subject to severe price competition. EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investment in ETPs: AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund. MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. NON-DIVERSIFICATION RISK:  The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities. PORTFOLIO TURNOVER RISK:  The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	NON-DIVERSIFICATION RISK:  The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad-based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Ultra Short Term Bond ETF | SPDR SSgA Ultra Short Term Bond ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets	0.20%	[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets	none	[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets	0.20%	[1]
YEAR 1	rr_ExpenseExampleYear01	$ 20
YEAR 3	rr_ExpenseExampleYear03	$ 64

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR SSgA Global Minimum Volatility ETF

SPDR SSgA Global Minimum Volatility ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Global Minimum Volatility ETF (the “Fund”) seeks to provide competitive long-term returns while maintaining low long-term volatility relative to the broad global market.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Global Minimum Volatility ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Global Minimum Volatility ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Global Minimum Volatility Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) utilizes a proprietary quantitative investment process to select a portfolio of equity securities that the Adviser believes will exhibit low volatility and provide competitive long-term returns relative to the broad global market. Volatility is a statistical measurement of the magnitude of up and down fluctuations in the value of a financial instrument or index over time. Volatility may result in rapid and dramatic price swings. The Portfolio will invest its assets in both U.S. and foreign investments. The Portfolio will generally invest at least 30% of its assets in securities of issuers economically tied to countries other than the United States and will generally hold securities of issuers economically tied to at least three countries, including the United States. The Adviser expects to favor securities with low exposure to market risk factors and low security-specific risk. The Adviser considers market risk factors to include, among others, a security’s size, momentum, value, liquidity, leverage and growth. While the Adviser attempts to manage the Fund’s volatility exposure to stabilize performance, there can be no guarantee that the Fund will reach its target volatility. Additionally, the Adviser implements risk constraints at the security, industry, size exposure, and sector levels. Through this quantitative process of security selection and portfolio diversification, the Adviser expects that the portfolio will be subject to a low level of absolute risk (as defined by standard deviation of returns) and thus should exhibit low volatility over the long term.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market.

FOREIGN INVESTMENT RISK: Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

EMERGING MARKETS RISK: Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shut down, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio’s and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR MFS Systematic Growth Equity ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR MFS Systematic Growth Equity ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR MFS Systematic Growth Equity ETF’s (the “Fund”) investment objective is to seek capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA MFS Systematic Growth Equity Portfolio (the "Portfolio"), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in equity securities. Equity securities in which the Portfolio invests include common stocks, preferred stocks and securities convertible into stocks. In selecting securities for the Portfolio, Massachusetts Financial Services Company (the "Sub-Adviser" or "MFS") utilizes a bottom-up approach to buying and selling investments for the Portfolio. Investments are selected based on fundamental and quantitative analysis. MFS uses fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions to identify potential investments. Factors considered may include analysis of an issuer's earnings, cash flows, competitive position, and management ability. MFS then uses quantitative models that systematically evaluate an issuer's valuation, price and earnings momentum, earnings quality, and other factors to determine which investments to buy and sell. While the Sub-Adviser may invest the Portfolio's assets in companies of any size, the Sub-Adviser generally focuses on companies with large market capitalizations. In selecting investments for the Portfolio, the Sub-Adviser invests the Portfolio's assets in the stocks of companies it believes have above average earnings growth potential compared to other companies (growth companies).
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. PREFERRED SECURITIES RISK: Generally, preferred security holders (such as the Portfolio) have no voting rights with respect to the issuing company unless certain events occur. In addition, preferred securities are subordinated to bonds and other debt instruments in a company's capital structure and therefore will be subject to greater credit risk than those debt instruments. Unlike debt securities, dividend payments on a preferred security typically must be declared by the issuer's board of directors. An issuer's board of directors is generally not under any obligation to pay a dividend (even if such dividends have accrued), and may suspend payment of dividends on preferred securities at any time. In the event an issuer of preferred securities experiences economic difficulties, the issuer's preferred securities may lose substantial value due to the reduced likelihood that the issuer's board of directors will declare a dividend and the fact that the preferred security may be subordinated to other securities of the same issuer. There is a chance that the issuer of any of the Portfolio's holdings will default (fail to make scheduled dividend payments on the preferred security or scheduled interest payments on other obligations of the issuer not held by the Portfolio). CONVERTIBLE SECURITIES RISK: Convertible securities are bonds, debentures, notes, preferred stocks or other securities that may be converted or exchanged (by the holder or by the issuer) into shares of the underlying common stock (or cash or securities of equivalent value) at a stated exchange ratio. Convertible securities tend to be subordinate to other debt securities issued by the same issuer so such securities may not receive full repayment in the event of an issuer default. Also, issuers of convertible securities are often not as strong financially as issuers with higher credit ratings. Convertible securities generally provide yields higher than the underlying stocks, but generally lower than comparable non-convertible securities. Because of this higher yield, convertible securities generally sell at a price above their "conversion value," which is the current market value of the stock to be received upon conversion. The difference between this conversion value and the price of convertible securities will vary over time depending on changes in the value of the underlying common stocks and interest rates. COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general. GROWTH RISK: The Portfolio emphasizes a "growth" style of investing. The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on "growth" securities may or may not move in tandem with the returns on other styles of investing or the overall stock market. LARGE CAP RISK: Returns on investments in stocks of large U.S. companies could trail the returns on investments in stocks of smaller and mid-sized companies. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Sub-Adviser's investment strategy may not produce the intended results and may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund's performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR MFS Systematic Growth Equity ETF | SPDR MFS Systematic Growth Equity ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Conservative Global Allocation ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR® SSgA Conservative Global Allocation ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Conservative Global Allocation ETF (the “Fund”) seeks to provide current income, capital preservation and the avoidance of excessive portfolio volatility.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Conservative Global Allocation Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide exposure to domestic and international debt and equity securities with a larger allocation to debt securities than to other asset classes. These fixed income securities tend to be less volatile than traditional equity securities. The Portfolio typically allocates approximately 60% of its assets to debt related securities, though this percentage can vary based on the Adviser’s tactical decisions. The allocations to each asset class will change over time as the Adviser’s expectations of each asset class shift. The Portfolio’s indirect holdings by virtue of investing in ETPs representing these asset classes consist of a diversified mix of domestic and international, including emerging market, equity securities across all market capitalizations, investment grade and high yield government and corporate bonds, inflation protected securities, mortgage pass through securities, commercial mortgage backed securities, asset backed securities, commodities and real estate investment trusts (“REITs”). The Portfolio, through its investments in ETPs, will generally invest at least 30% of its assets in securities of issuers economically tied to countries other than the United States and will generally hold securities of issuers economically tied to at least three countries, including the United States. In determining if a security is economically tied to a non-U.S. country, the Portfolio generally looks to the country of incorporation of the issuer as listed on Bloomberg, a widely recognized provider of market information. However, the Adviser may determine a security is economically tied to a non-U.S. country based on other factors, such as an issuer’s country of domicile, where more than 50% of an issuer’s revenues are generated or where an issuer’s primary exchange is located. As a result, a security may be economically tied to more than one country. ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); exchange traded commodity trusts; and exchange traded notes (“ETNs”). The Portfolio may invest in ETPs that are qualified publicly traded partnerships (“QPTPs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs: EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income. FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative. COMMODITIES RISK:  Exposure to the commodities markets may subject the Portfolio to greater volatility than investments in traditional securities. Commodities are subject to substantial price fluctuations over short periods of time and may be affected by unpredictable economic, political and environmental events. Factors that may significantly affect the prices of commodities include, but are not limited to: global supply and demand; domestic and international interest rates and investors’ expectations of interest rates; inflation rates and investors’ expectations of inflation rates; the investment and trading activities of commodity futures contracts; political, economic, or financial events, both globally and regionally. TAX RISK:  Regulated investment companies are subject to favorable tax treatment under the Internal Revenue Code. To qualify as a regulated investment company, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. Thus, income from the Portfolio’s investments in certain commodities-related investments may cause the Fund not to qualify as a regulated investment company. The Portfolio may invest up to 25% of its total assets in one or more ETPs that are QPTPs and whose principal activities are the buying and selling of commodities or options, futures, or forwards with respect to commodities. Income from QPTPs is generally qualifying income. If an ETP fails to qualify as a QPTP, the income generated from the Portfolio’s investment in the ETP may not be qualifying income. The Portfolio will only invest in such an ETP if it intends to qualify as a QPTP, but there is no guarantee that each such ETP will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of such ETPs as QPTPs. If the Fund fails to qualify as a regulated investment company, the Fund will be subject to tax, which will reduce returns to shareholders. Such a failure will also alter the treatment of distributions to shareholders. HIGH YIELD SECURITIES RISK:  Securities rated below investment grade, commonly referred to as “junk bonds,” include bonds that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Adviser, and may involve greater risks than securities in higher rating categories. Such bonds are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities without taking a discount, which could be significant. High yield securities also may present greater credit risk because such securities may be issued in connection with corporate restructuring by highly leveraged issuers or may not be current in the payment of interest or principal or in default. U.S. GOVERNMENT AGENCY SECURITIES RISK:  Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, the performance of the Portfolio and, therefore, the Fund will be adversely impacted. PREPAYMENT RISK:  Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income. MORTGAGE-BACKED SECURITIES RISK:  Mortgage-backed securities, other than Government National Mortgage Association (“GNMA”) mortgage-backed securities, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. Mortgage-backed securities tend to increase in value less than other debt securities when interest rates decline, but are subject to similar risk of decline in market value during periods of rising interest rates. Because of prepayment and extension risk, mortgage-backed securities react differently to changes in interest rates than other bonds. Small movements in interest rates (both increases and decreases) may quickly and significantly affect the value of certain mortgage-backed securities. MORTGAGE PASS-THROUGH SECURITIES RISK:  Most transactions in mortgage pass-through securities occur through standardized contracts for future delivery in which the exact mortgage pools to be delivered are not specified until a few days prior to settlement, referred to as a “to-be-announced transaction” or “TBA Transaction.” In a TBA Transaction, the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount and price. Default by or bankruptcy of a counterparty to a TBA Transaction would expose the Portfolio to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA Transaction. REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act. MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not commenced operations as of the date of this Prospectus and therefore the Fund does not have a full calendar year of performance information.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not commenced operations as of the date of this Prospectus and therefore the Fund does not have a full calendar year of performance information.
SPDR SSgA Conservative Global Allocation ETF | SPDR SSgA Conservative Global Allocation ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets	0.35%	[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets	none	[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets	0.35%	[1]
YEAR 1	rr_ExpenseExampleYear01	$ 36
YEAR 3	rr_ExpenseExampleYear03	$ 113

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR MFS Systematic Growth Equity ETF

SPDR MFS Systematic Growth Equity ETF

INVESTMENT OBJECTIVE

The SPDR MFS Systematic Growth Equity ETF’s (the “Fund”) investment objective is to seek capital appreciation.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR MFS Systematic Growth Equity ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR MFS Systematic Growth Equity ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA MFS Systematic Growth Equity Portfolio (the "Portfolio"), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in equity securities. Equity securities in which the Portfolio invests include common stocks, preferred stocks and securities convertible into stocks.

In selecting securities for the Portfolio, Massachusetts Financial Services Company (the "Sub-Adviser" or "MFS") utilizes a bottom-up approach to buying and selling investments for the Portfolio. Investments are selected based on fundamental and quantitative analysis. MFS uses fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions to identify potential investments. Factors considered may include analysis of an issuer's earnings, cash flows, competitive position, and management ability. MFS then uses quantitative models that systematically evaluate an issuer's valuation, price and earnings momentum, earnings quality, and other factors to determine which investments to buy and sell.

While the Sub-Adviser may invest the Portfolio's assets in companies of any size, the Sub-Adviser generally focuses on companies with large market capitalizations. In selecting investments for the Portfolio, the Sub-Adviser invests the Portfolio's assets in the stocks of companies it believes have above average earnings growth potential compared to other companies (growth companies).

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

PREFERRED SECURITIES RISK: Generally, preferred security holders (such as the Portfolio) have no voting rights with respect to the issuing company unless certain events occur. In addition, preferred securities are subordinated to bonds and other debt instruments in a company's capital structure and therefore will be subject to greater credit risk than those debt instruments. Unlike debt securities, dividend payments on a preferred security typically must be declared by the issuer's board of directors. An issuer's board of directors is generally not under any obligation to pay a dividend (even if such dividends have accrued), and may suspend payment of dividends on preferred securities at any time. In the event an issuer of preferred securities experiences economic difficulties, the issuer's preferred securities may lose substantial value due to the reduced likelihood that the issuer's board of directors will declare a dividend and the fact that the preferred security may be subordinated to other securities of the same issuer. There is a chance that the issuer of any of the Portfolio's holdings will default (fail to make scheduled dividend payments on the preferred security or scheduled interest payments on other obligations of the issuer not held by the Portfolio).

CONVERTIBLE SECURITIES RISK: Convertible securities are bonds, debentures, notes, preferred stocks or other securities that may be converted or exchanged (by the holder or by the issuer) into shares of the underlying common stock (or cash or securities of equivalent value) at a stated exchange ratio. Convertible securities tend to be subordinate to other debt securities issued by the same issuer so such securities may not receive full repayment in the event of an issuer default. Also, issuers of convertible securities are often not as strong financially as issuers with higher credit ratings. Convertible securities generally provide yields higher than the underlying stocks, but generally lower than comparable non-convertible securities. Because of this higher yield, convertible securities generally sell at a price above their "conversion value," which is the current market value of the stock to be received upon conversion. The difference between this conversion value and the price of convertible securities will vary over time depending on changes in the value of the underlying common stocks and interest rates.

COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general.

GROWTH RISK: The Portfolio emphasizes a "growth" style of investing. The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on "growth" securities may or may not move in tandem with the returns on other styles of investing or the overall stock market.

LARGE CAP RISK: Returns on investments in stocks of large U.S. companies could trail the returns on investments in stocks of smaller and mid-sized companies.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Sub-Adviser's investment strategy may not produce the intended results and may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund's performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

SPDR SSgA Risk Aware ETF

FUND SUMMARIES

SPDR SSgA Risk Aware ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Risk Aware ETF (the “Fund”) seeks to provide competitive returns compared to the broad U.S. equity market and capital appreciation.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Risk Aware ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Risk Aware ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Risk Aware Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

In seeking its objective, the Portfolio invests in a diversified selection of equity securities included in the Russell 3000 Index that SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) believes are aligned with predicted investor risk preferences. In selecting securities for the Portfolio, the Adviser utilizes a proprietary quantitative investment process to measure and predict investor risk preferences. This process reflects the multidimensional and time-varying nature of risk, as stock characteristics the market deems to be safe or risky change over time. As a result, different periods of predicted uncertainty may result in portfolios that are more defensive or risk-seeking, depending on what the market considers safe and/or risky at each juncture (in light of factors such as beta, size, credit risk, credit spreads, exposure to gold, U.S. dollar exchange rates, and implied volatility). During periods of anticipated high risk, the Adviser will adjust the Portfolio’s composition to be defensive and may increase exposure to large cap and/or value companies. During periods of anticipated low risk, the Adviser will adjust the Portfolio’s composition to be risk-seeking and may increase exposure to small cap and/or growth companies. In periods of anticipated moderate risk, the Portfolio’s composition will more closely reflect the weighted composition of the Russell 3000 Index and may have increased exposure to mid cap companies. Due to on-going market fluctuations, the Adviser believes the resulting ebbing and flowing of risk preferences give this strategy the potential to provide competitive returns relative to the Russell 3000 Index over the long term. The Portfolio is non-diversified for purposes of the Investment Company Act of 1940, and as a result may invest a greater percentage of its assets in a particular issuer than a diversified fund. However, the Portfolio expects to have exposure to a diversified mix of equity securities.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general.

FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.

LARGE CAP RISK: Returns on investments in stocks of large companies could trail the returns on investments in stocks of smaller and mid-sized companies.

MID CAP RISK: Mid-sized companies may be more volatile and more likely than large-capitalization companies to have relatively limited product lines, markets or financial resources, or depend on a few key employees. Returns on investments in stocks of mid-size companies could trail the returns on investments in stocks of larger or smaller companies.

SMALL CAP RISK: Small-sized companies may be more volatile and more likely than large- and mid-capitalization companies to have relatively limited product lines, markets or financial resources, or depend on a few key employees. Returns on investments in stocks of small companies could trail the returns on investments in stocks of larger companies.

GROWTH RISK: The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on “growth” securities may or may not move in tandem with the returns on other styles of investing or the overall stock market.

VALUE RISK: A “value” style of investing emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR SSgA Conservative Ultra Short Bond ETF

SPDR SSgA Conservative Ultra Short Term Bond ETF

INVESTMENT OBJECTIVE

The SPDR SSgA Conservative Ultra Short Term Bond ETF (the “Fund”) seeks to provide current income consistent with preservation of capital and daily liquidity through short duration high quality investments with the avoidance of excessive portfolio volatility.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR SSgA Conservative Ultra Short Bond ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR SSgA Conservative Ultra Short Bond ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Conservative Ultra Short Term Bond Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests, under normal circumstances, at least 80% of the Portfolio’s net assets (plus the amount of borrowings for investment purposes) in a diversified portfolio of U.S. dollar-denominated investment grade fixed income securities. The Portfolio primarily invests in investment grade fixed income securities that are rated a minimum of A- or higher by Standard & Poor’s Financial Services LLC and/or Fitch Inc., or A3 or higher by Moody’s Investors Service, Inc., or, if unrated, determined by the management team to be of equivalent quality. The Portfolio invests in fixed and floating rate securities of varying maturities, such as corporate obligations (including commercial paper of U.S. and foreign entities, master notes, and medium term notes); government bonds (including U.S. Treasury Bills, notes, and bonds); agency securities; privately-issued securities; asset-backed and mortgage-backed securities; money market instruments (including U.S. and foreign bank time deposits, certificates of deposit, and banker acceptances) and other investment companies. The Portfolio may also invest in exchange traded products (“ETPs”). ETPs include exchange traded funds registered under the Investment Company Act of 1940, as amended, (the “1940 Act”) that seek to track the performance of a market index (“Underlying ETFs”) and exchange traded notes. In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.

Under normal circumstances, the effective duration of the Portfolio is expected to be four months or less. Effective duration is a measure of the Portfolio’s price sensitivity to changes in yields or interest rates; however, investors should be aware that effective duration is not an exact measurement and may not reliably predict a particular security’s price sensitivity to changes in yield or interest rates. In addition, the Portfolio expects to maintain a weighted average maturity between six and eighteen months. Weighted average maturity is a U.S. dollar-weighted average of the remaining term to maturity of the underlying securities in the Portfolio. For the purposes of determining the Portfolio’s weighted average maturity, a security’s final maturity date, or for amortizing securities such as asset-backed and mortgage-backed securities, its weighted average life will be used for calculation purposes. The Portfolio and Fund are not money market funds and do not seek to maintain a stable net asset value of $1.00 per share.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

DEBT SECURITIES INVESTING RISK: The value of debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income.

FLOATING RATE NOTES INVESTING RISK: Floating rate notes protect investors against a rise in interest rates, but also carry lower yields than fixed notes of the same maturity. The interest rate for a floating rate note resets or adjusts periodically (normally on a daily, monthly, quarterly or semiannual basis by reference to a base lending rate (such as LIBOR). Because rates on floating rate notes reset only periodically, changes in prevailing interest rates (particularly sudden and significant changes) can be expected to cause fluctuations in net asset value. Floating rate notes generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Portfolio needs to liquidate such loans.

U.S. TREASURY OBLIGATIONS RISK: Treasury obligations may differ from other fixed income securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the United States may cause the value of its Treasury obligations to decline.

U.S. GOVERNMENT AGENCY SECURITIES RISK: Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, performance will be adversely impacted.

SOVEREIGN OBLIGATIONS RISK: The Portfolio invests in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations.

ASSET-BACKED AND MORTGAGE-BACKED SECURITIES RISK: Asset-backed and mortgage-backed securities (residential and commercial) represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. These securities, in most cases, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. These securities are subject to the risk of default on the underlying asset or mortgage, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities.

PREPAYMENT RISK: Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income.

PRIVATELY-ISSUED SECURITIES RISK. The Portfolio will invest in privately-issued securities, including those which are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act of 1933, as amended (the “1933 Act”). Privately-issued securities are securities that have not been registered under the 1933 Act and as a result are subject to legal restrictions on resale. Privately-issued securities are not traded on established markets and may be illiquid, difficult to value and subject to wide fluctuations in value. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Portfolio from disposing of them promptly at reasonable prices.

DERIVATIVES RISK: A derivative is a financial contract the value of which depends on, or is derived from, the value of a financial asset (such as stock, bond or currency), a physical asset (such as gold) or a market index (such as the S&P 500 Index). The Fund may invest in forward foreign currency contracts. Forward foreign currency contracts involve an obligation to purchase or sell a specific amount of currency at a future date or date range at a specific price, thereby fixing the exchange rate for a specified time in the future. When used for hedging purposes, forward foreign currency contracts tend to limit any potential gain that may be realized if the value of the Fund’s foreign holdings increases because of currency fluctuations. Compared to conventional securities, derivatives can be more sensitive to changes in interest rates or to sudden fluctuations in market prices and thus the Fund’s losses may be greater if it invests in derivatives than if it invests only in conventional securities.

FOREIGN INVESTMENT RISK: Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

FINANCIAL SECTOR RISK: Financial services companies are subject to extensive governmental regulation which may limit both the amounts and types of loans and other financial commitments they can make, and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change or due to increased competition. In addition, the recent deterioration of the credit markets generally has caused an adverse impact in a broad range of markets, including U.S. and international credit and interbank money markets generally, thereby affecting a wide range of financial institutions and markets. Recent events in the financial sector have resulted, and may continue to result, in an unusually high degree of volatility in the financial markets, both domestic and foreign, and cause certain financial services companies to incur large losses. Numerous financial services companies have experienced substantial declines in the valuations of their assets, taken action to raise capital (such as the issuance of debt or equity securities), or even ceased operations. These actions have caused the securities of many financial services companies to experience a dramatic decline in value. Credit losses resulting from financial difficulties of borrowers and financial losses associated with investment activities can negatively impact the sector. Insurance companies may be subject to severe price competition.

EXCHANGE TRADED PRODUCTS RISK: The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an exchange traded note (“ETN”) may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs:

AFFILIATED ETP RISK: The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

NON-DIVERSIFICATION RISK: The Fund is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio’s and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Risk Aware ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	FUND SUMMARIES SPDR SSgA Risk Aware ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Risk Aware ETF (the “Fund”) seeks to provide competitive returns compared to the broad U.S. equity market and capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Risk Aware Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. In seeking its objective, the Portfolio invests in a diversified selection of equity securities included in the Russell 3000 Index that SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) believes are aligned with predicted investor risk preferences. In selecting securities for the Portfolio, the Adviser utilizes a proprietary quantitative investment process to measure and predict investor risk preferences. This process reflects the multidimensional and time-varying nature of risk, as stock characteristics the market deems to be safe or risky change over time. As a result, different periods of predicted uncertainty may result in portfolios that are more defensive or risk-seeking, depending on what the market considers safe and/or risky at each juncture (in light of factors such as beta, size, credit risk, credit spreads, exposure to gold, U.S. dollar exchange rates, and implied volatility). During periods of anticipated high risk, the Adviser will adjust the Portfolio’s composition to be defensive and may increase exposure to large cap and/or value companies. During periods of anticipated low risk, the Adviser will adjust the Portfolio’s composition to be risk-seeking and may increase exposure to small cap and/or growth companies. In periods of anticipated moderate risk, the Portfolio’s composition will more closely reflect the weighted composition of the Russell 3000 Index and may have increased exposure to mid cap companies. Due to on-going market fluctuations, the Adviser believes the resulting ebbing and flowing of risk preferences give this strategy the potential to provide competitive returns relative to the Russell 3000 Index over the long term. The Portfolio is non-diversified for purposes of the Investment Company Act of 1940, and as a result may invest a greater percentage of its assets in a particular issuer than a diversified fund. However, the Portfolio expects to have exposure to a diversified mix of equity securities.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general. FACTOR RISK: The market may reward certain factors for a period of time and not others. By way of example, during periods of risk-seeking, credit risk and volatility may be rewarded while during defensive periods, exposure to gold may be rewarded. The returns for a specific factor may vary significantly relative to other factors and may increase or decrease significantly during different phases of an economic cycle. If the Portfolio was overweight in factors viewed unfavorably by the market and/or the Portfolio was underweight in factors being rewarded by the market, the Portfolio would underperform relative to the market. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance. LARGE CAP RISK: Returns on investments in stocks of large companies could trail the returns on investments in stocks of smaller and mid-sized companies. MID CAP RISK: Mid-sized companies may be more volatile and more likely than large-capitalization companies to have relatively limited product lines, markets or financial resources, or depend on a few key employees. Returns on investments in stocks of mid-size companies could trail the returns on investments in stocks of larger or smaller companies. SMALL CAP RISK: Small-sized companies may be more volatile and more likely than large- and mid-capitalization companies to have relatively limited product lines, markets or financial resources, or depend on a few key employees. Returns on investments in stocks of small companies could trail the returns on investments in stocks of larger companies. GROWTH RISK: The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on “growth” securities may or may not move in tandem with the returns on other styles of investing or the overall stock market. VALUE RISK: A “value” style of investing emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	NON-DIVERSIFICATION RISK: The Portfolio is non-diversified and may invest a larger percentage of its assets in securities of a few issuers or a single issuer than that of a diversified fund. As a result, the Portfolio’s and, therefore, the Fund’s performance may be disproportionately impacted by the performance of relatively few securities.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR SSgA Risk Aware ETF | SPDR SSgA Risk Aware ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR MFS Systematic Value Equity ETF

SPDR MFS Systematic Value Equity ETF

INVESTMENT OBJECTIVE

The SPDR MFS Systematic Value Equity ETF’s (the “Fund”) investment objective is to seek capital appreciation.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR MFS Systematic Value Equity ETF
MANAGEMENT FEES	[1][2]
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1][4]
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR MFS Systematic Value Equity ETF

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the SSgA MFS Systematic Value Equity Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in equity securities. Equity securities in which the Portfolio invests include common stocks, preferred stocks and securities convertible into stocks.

In selecting securities for the Portfolio, Massachusetts Financial Services Company (the “Sub-Adviser” or “MFS”) utilizes a bottom-up approach to buying and selling investments for the Portfolio. Investments are selected based on fundamental and quantitative analysis. MFS uses fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions to identify potential investments. Factors considered may include analysis of an issuer’s earnings, cash flows, competitive position, and management ability. MFS then uses quantitative models that systematically evaluate an issuer’s valuation, price and earnings momentum, earnings quality, and other factors to determine which investments to buy and sell.

While the Sub-Adviser may invest the Portfolio’s assets in companies of any size, the Sub-Adviser generally focuses on companies with large market capitalizations. In selecting investments for the Portfolio, the Sub-Adviser invests the Portfolio’s assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies).

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices.

PREFERRED SECURITIES RISK: Generally, preferred security holders (such as the Portfolio) have no voting rights with respect to the issuing company unless certain events occur. In addition, preferred securities are subordinated to bonds and other debt instruments in a company’s capital structure and therefore will be subject to greater credit risk than those debt instruments. Unlike debt securities, dividend payments on a preferred security typically must be declared by the issuer’s board of directors. An issuer’s board of directors is generally not under any obligation to pay a dividend (even if such dividends have accrued), and may suspend payment of dividends on preferred securities at any time. In the event an issuer of preferred securities experiences economic difficulties, the issuer’s preferred securities may lose substantial value due to the reduced likelihood that the issuer’s board of directors will declare a dividend and the fact that the preferred security may be subordinated to other securities of the same issuer. There is a chance that the issuer of any of the Portfolio’s holdings will default (fail to make scheduled dividend payments on the preferred security or scheduled interest payments on other obligations of the issuer not held by the Portfolio).

CONVERTIBLE SECURITIES RISK: Convertible securities are bonds, debentures, notes, preferred stocks or other securities that may be converted or exchanged (by the holder or by the issuer) into shares of the underlying common stock (or cash or securities of equivalent value) at a stated exchange ratio. Convertible securities tend to be subordinate to other debt securities issued by the same issuer so such securities may not receive full repayment in the event of an issuer default. Also, issuers of convertible securities are often not as strong financially as issuers with higher credit ratings. Convertible securities generally provide yields higher than the underlying stocks, but generally lower than comparable non-convertible securities. Because of this higher yield, convertible securities generally sell at a price above their “conversion value,” which is the current market value of the stock to be received upon conversion. The difference between this conversion value and the price of convertible securities will vary over time depending on changes in the value of the underlying common stocks and interest rates.

COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general.

VALUE RISK: The Portfolio employs a “value” style of investing that emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market.

LARGE CAP RISK: Returns on investments in stocks of large U.S. companies could trail the returns on investments in stocks of smaller and mid-sized companies.

MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Sub-Adviser’s investment strategy may not produce the intended results and may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective.

PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

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SPDR Blackstone / GSO Senior Loan ETF

SPDR^® Blackstone/GSO Senior Loan ETF

INVESTMENT OBJECTIVE

The investment objective of the SPDR Blackstone/GSO Senior Loan ETF (the “Fund”) is to provide current income consistent with the preservation of capital.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		SPDR Blackstone / GSO Senior Loan ETF
MANAGEMENT FEES	[1][2]	0.90%
DISTRIBUTION AND SERVICE (12b-1) FEES	[1][3]	none
OTHER EXPENSES	[1]	none
TOTAL ANNUAL FUND OPERATING EXPENSES	[1]	0.90%

EXAMPLE:

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	YEAR 1	YEAR 3
SPDR Blackstone / GSO Senior Loan ETF	92	287

PORTFOLIO TURNOVER:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the period from the commencement of the Fund’s operations (April 3, 2013) to the end of the most recent fiscal year, the Fund’s portfolio turnover rate was 4% of the average value of its portfolio.

THE FUND’S PRINCIPAL INVESTMENT STRATEGY

Under normal circumstances, the Fund invests substantially all of its assets in the Blackstone/GSO Senior Loan Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio.

In pursuing its investment objective, the Portfolio seeks to outperform the Markit iBoxx USD Liquid Leveraged Loan Index (the “Primary Index”) and the S&P/LSTA U.S. Leveraged Loan 100 Index (the “Secondary Index”) by normally investing at least 80% of its net assets (plus any borrowings for investment purposes) in Senior Loans. For purposes of this 80% test, “Senior Loans” are first lien senior secured floating rate bank loans. A Senior Loan is an advance or commitment of funds made by one or more banks or similar financial institutions, including the Portfolio, to one or more corporations, partnerships or other business entities and pays interest at a floating or adjusting rate that is determined periodically at a designated premium above a base lending rate, most commonly the London Interbank Offered Rate (“LIBOR”). A Senior Loan is senior to all unsecured claims against the borrower and senior or equal to all other secured claims, meaning that, in the event of a bankruptcy, the Senior Loan, together with other first lien claims, is entitled to be the first to be repaid out of proceeds of the assets securing the loans, before other existing claims or interests receive repayment. However, in bankruptcy proceedings, there may be other claims, such as taxes or additional advances that take precedence. The Primary Index is composed of the 100 most liquid Senior Loans in the market, while the Secondary Index is composed of the 100 largest Senior Loans in the market, as measured by the borrowed amounts outstanding. The Portfolio intends to hold a large percentage of the components of the Primary and Secondary Indexes. It is anticipated that the Portfolio will invest approximately 50% to 75% of its net assets in Senior Loans that are eligible for inclusion in the Primary and/or Secondary Indexes. Each of the Portfolio’s Senior Loan investments is expected to have no less than $250 million par outstanding.

The Portfolio invests in Senior Loans that are made predominantly to businesses operating in North America, but may also invest in Senior Loans made to businesses operating outside of North America. The Portfolio may invest in Senior Loans directly, either from the borrower as part of a primary issuance or in the secondary market through assignments of portions of Senior Loans from third parties, or participations in Senior Loans, which are contractual relationships with an existing lender in a loan facility whereby the Portfolio purchases the right to receive principal and interest payments on a loan but the existing lender remains the record holder of the loan. Under normal market conditions, the Portfolio expects to maintain an average duration of less than 90 days.

In selecting securities for the Portfolio, the Portfolio’s sub-adviser, GSO/Blackstone Debt Funds Management LLC (the “Sub-Adviser”), seeks to construct a portfolio of loans that it believes is less volatile than the general loan market. In addition, when making investments, the Sub-Adviser seeks to maintain appropriate liquidity and price transparency for the Portfolio. On an on-going basis, the Sub-Adviser adds or removes those individual loans that it believes will cause the Portfolio to outperform or underperform, respectively, the Primary and Secondary Indexes.

When identifying prospective investment opportunities in Senior Loans, the Sub-Adviser currently intends to invest principally in Senior Loans that are below investment grade quality and will rely on fundamental credit analysis in an effort to attempt to minimize the loss of the Portfolio’s capital. While credit ratings assigned by Moody’s Investors Services, Inc., Standard & Poor’s, Inc. and/or Fitch Inc. (the “SROs” (statistical rating agencies)) will be considered, such ratings will not be determinative in the Sub-Adviser’s process in the selection of specific debt securities (including Senior Loans). The Senior Loans and other securities that the Sub-Adviser is likely to select for investment in by the Portfolio will typically be rated below investment grade quality by one or more of the SROs or, if unrated, will typically, in the opinion of the Sub-Adviser, be of similar credit quality. If circumstances cause the Sub-Adviser to take a negative credit view on an existing investment the Portfolio may, if the Sub-Adviser believes that circumstances require, exit the investment. The circumstances giving rise to the Sub-Adviser’s negative credit view may, but will not necessarily, coincide with a downgrade of the Senior Loan or other security’s credit rating. The Sub-Adviser expects to invest in Senior Loans, other loans and bonds of companies, including high yield securities, possessing the following attributes, which it believes will help generate higher risk adjusted total returns:

Leading, defensible market positions.  The Sub-Adviser intends to invest in companies that it believes have developed strong positions within their respective markets and exhibit the potential to maintain sufficient cash flows and profitability to service their obligations in a range of economic environments. The Sub-Adviser will seek companies that it believes possess advantages in scale, scope, customer loyalty, product pricing, or product quality versus their competitors, thereby minimizing business risk and protecting profitability.

Investing in companies with positive cash flow.  The Sub-Adviser intends to invest primarily in established companies which have demonstrated a record of profitability and cash flows over several economic cycles. The Sub-Adviser believes such companies are well-positioned to maintain consistent cash flow to service and repay their obligations and maintain growth in their businesses or market share. The Sub-Adviser does not intend to invest in primarily start-up companies, companies in turnaround situations or companies with speculative business plans.

Proven management teams.  The Sub-Adviser intends to focus on investments in which the target company has an experienced management team with an established track record of success. The Sub-Adviser will typically require companies to have in place proper incentives to align management’s goals with the Portfolio’s goals.

Private equity sponsorship.  Often the Sub-Adviser will seek to participate in transactions sponsored by what it believes to be high-quality private equity firms. The Sub-Adviser believes that a private equity sponsor’s willingness to invest significant sums of equity capital into a company is an implicit endorsement of the quality of the investment. Further, private equity sponsors of companies with significant investments at risk have the ability and a strong incentive to contribute additional capital in difficult economic times should operational issues arise.

Diversification, concentration and reliance on other lenders.  The Sub-Adviser will seek to invest broadly among companies and industries, thereby potentially reducing the risk of a downturn in any one company or industry having a disproportionate impact on the value of the Portfolio’s portfolio. While the Portfolio does not treat banks originating loans as the issuers of such loans, it is possible that under a different interpretation the Portfolio may be deemed to concentrate its investments in the financial services industries. Loans, and the collateral securing them, are typically monitored by agents for the lenders, which may be the originating bank or banks. The Portfolio may be affected by the creditworthiness of the agent bank and other intermediate participants in a Senior Loan, in addition to the borrower, since rights that may exist under the loan against the borrower if the borrower defaults are typically asserted by or through the agent bank or intermediate participant. Agents are typically large commercial banks, although for Senior Loans that are not broadly syndicated they can also include thrift institutions, insurance companies or finance companies (or their affiliates). Such companies may be especially susceptible to the effects of changes in interest rates resulting from changes in U.S. or foreign fiscal or monetary policies, governmental regulations affecting capital raising activities or other economic or market fluctuations.

PRINCIPAL RISKS OF INVESTING IN THE FUND

As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests.

SENIOR LOAN RISK:  Investments in Senior Loans are subject to credit risk and general investment risk. Credit risk refers to the possibility that the borrower of a Senior Loan will be unable and/or unwilling to make timely interest payments and/or repay the principal on its obligation. Default in the payment of interest or principal on a Senior Loan will result in a reduction in the value of the Senior Loan and consequently a reduction in the value of the Portfolio’s investments and a potential decrease in the net asset value (“NAV”) of the Portfolio. Senior Loans are also subject to the risk that the value of the collateral securing a Senior Loan may decline, be insufficient to meet the obligations of the borrower or be difficult to liquidate. In addition, the Portfolio’s access to the collateral may be limited by bankruptcy or other insolvency laws. Some Senior Loans are subject to the risk that a court, pursuant to fraudulent conveyance or other similar laws, could subordinate the Senior Loans to presently existing or future indebtedness of the borrower or take other action detrimental to lenders, including the Portfolio, such as invalidation of Senior Loans or causing interest previously paid to be refunded to the borrower. Senior Loans are also subject to high yield securities risks and liquidity risks described below.

HIGH YIELD SECURITIES RISK:  The securities (including bank loans) in which the Portfolio primarily invests will typically be rated below investment grade. Securities rated below investment grade, commonly referred to as “junk bonds” or “high yield” securities, include securities that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Sub-Adviser, and may involve greater risks than securities in higher rating categories. Such securities are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” or “high yield” securities may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities or could result in lower prices than those used in calculating the Portfolio’s net asset value. Because of the substantial risks associated with investments in lower grade securities, investors could lose money on their investment in Shares of the Fund, both in the short-term and the long-term.

LIQUIDITY RISK:  There is no organized exchange on which loans are traded and reliable market quotations may not be readily available. A majority of the Portfolio’s assets are likely to be invested in loans that are less liquid than securities traded on national exchanges. Loans with reduced liquidity involve greater risk than securities with more liquid markets. Available market quotations for such loans may vary over time, and if the credit quality of a loan unexpectedly declines, secondary trading of that loan may decline for a period of time. During periods of infrequent trading, valuing a loan can be more difficult and buying and selling a loan at an acceptable price can be more difficult and delayed. In the event that the Portfolio voluntarily or involuntarily liquidates portfolio assets during periods of infrequent trading, it may not receive full value for those assets. Therefore, elements of judgment may play a greater role in valuation of loans. To the extent that a secondary market exists for certain loans, the market may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods.

FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors.

FUND PERFORMANCE

The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Jun. 30, 2013
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Central Index Key	dei_EntityCentralIndexKey	0001516212
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Oct. 28, 2013
Document Effective Date	dei_DocumentEffectiveDate	Oct. 31, 2013
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR SSgA Aggressive Global Allocation ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR® SSgA Aggressive Global Allocation ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR SSgA Aggressive Global Allocation ETF (the “Fund”) seeks to provide capital appreciation,
Objective, Secondary [Text Block]	rr_ObjectiveSecondaryTextBlock	with a secondary emphasis on current income.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA Aggressive Global Allocation Portfolio (the “Portfolio”), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. SSgA Funds Management, Inc. (the “Adviser” or “SSgA FM”) invests the assets of the Portfolio among exchange traded products (“ETPs”) that provide exposure to domestic and international debt and equity securities with a larger allocation to equity securities than to other asset classes. These equity securities tend to be more volatile than traditional fixed income securities. The Portfolio typically allocates approximately 80% or more of its assets to equity securities, though this percentage can vary based on the Adviser’s tactical decisions. The Portfolio’s indirect holdings by virtue of investing in ETPs representing these asset classes consist of a diversified mix of domestic and international, including emerging market, equity securities across all market capitalizations, investment grade and high yield government and corporate bonds, inflation protected securities, mortgage pass through securities, commercial mortgage backed securities, asset backed securities, commodities and real estate investment trusts (“REITs”). The Portfolio, through its investments in ETPs, will generally invest at least 30% of its assets in securities of issuers economically tied to countries other than the United States and will generally hold securities of issuers economically tied to at least three countries, including the United States. In determining if a security is economically tied to a non-U.S. country, the Portfolio generally looks to the country of incorporation of the issuer as listed on Bloomberg, a widely recognized provider of market information. However, the Adviser may determine a security is economically tied to a non-U.S. country based on other factors, such as an issuer’s country of domicile, where more than 50% of an issuer’s revenues are generated or where an issuer’s primary exchange is located. As a result, a security may be economically tied to more than one country. ETPs in which the Portfolio invests include exchange traded funds registered under the Investment Company Act of 1940, as amended (the “1940 Act”) (“Underlying ETFs”); exchange traded commodity trusts; and exchange traded notes (“ETNs”). The Portfolio may invest in ETPs that are qualified publicly traded partnerships (“QPTPs”). In addition, the Portfolio may invest in certain ETPs that pay fees to the Adviser and its affiliates for management, marketing or other services.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EXCHANGE TRADED PRODUCTS RISK:  The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which the Portfolio invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an ETF’s shares) for a number of reasons. For example, supply and demand for shares of an Underlying ETF or market disruptions may cause the market price of the Underlying ETF to deviate from the value of the Underlying ETF’s investments, which may be exacerbated in less liquid markets. The value of an ETN may also differ from the valuation of its reference market due to changes in the issuer’s credit rating. By investing in ETPs, the Fund indirectly bears the Portfolio’s proportionate share of any fees and expenses (e.g. management, custody, accounting, and administration) of the ETP, if applicable, in addition to the fees and expenses that the Fund and its shareholders directly bear in connection with the Portfolio’s and the Fund’s operations. The Portfolio, and indirectly the Fund, is subject to the following risks indirectly through its investments in ETPs: EQUITY INVESTING RISK:  The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. DEBT SECURITIES INVESTING RISK:  The value of the debt securities may increase or decrease as a result of the following: market fluctuations, increases in interest rates, inability of issuers to repay principal and interest or illiquidity in the debt securities markets; the risk of low rates of return due to reinvestment of securities during periods of falling interest rates or repayment by issuers with higher coupon or interest rates; and/or the risk of low income due to falling interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. This may result in a reduction in income from debt securities income. FOREIGN INVESTMENT RISK:  Foreign investments involve certain risks that are greater than those associated with investments in securities of U.S. issuers. Returns on investments in foreign securities could be more volatile than, or trail the returns on, investments in U.S. securities. Investments in securities issued by entities based outside the United States pose distinct risks since political and economic events unique to a country or region will affect those markets and their issuers. Further, such entities and/or their securities may also be affected by currency controls; different accounting, auditing, financial reporting, and legal standards and practices; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. In addition, the value of a local currency could decline relative to the value of the U.S. dollar, which may affect the value of the investment to U.S. investors. EMERGING MARKETS RISK:  Investment in emerging markets involves greater risk of loss than investments in a developed market. This is due to, among other things, greater market volatility, lower trading volume, political and economic instability, high levels of inflation, deflation or currency devaluation, greater risk of market shutdown, and more governmental limitations on foreign investment policy than those typically found in a developed market. In addition, the financial stability of issuers (including governments) in emerging market countries may be more precarious than in other countries. As a result, there will tend to be an increased risk of price volatility associated with investments in issuers domiciled in emerging market countries, which may be magnified by currency fluctuations relative to the U.S. dollar. Settlement practices for transactions in foreign markets may differ from those in U.S. markets. Such differences include delays beyond periods customary in the United States and practices, such as delivery of securities prior to receipt of payment, which increase the likelihood of a “failed settlement.” Failed settlements could result in losses to the Portfolio. For these and other reasons, investments in emerging markets are often considered speculative. COMMODITIES RISK:  Exposure to the commodities markets may subject the Portfolio to greater volatility than investments in traditional securities. Commodities are subject to substantial price fluctuations over short periods of time and may be affected by unpredictable economic, political and environmental events. Factors that may significantly affect the prices of commodities include, but are not limited to: global supply and demand; domestic and international interest rates and investors’ expectations of interest rates; inflation rates and investors’ expectations of inflation rates; the investment and trading activities of commodity futures contracts; political, economic, or financial events, both globally and regionally. TAX RISK:  Regulated investment companies are subject to favorable tax treatment under the Internal Revenue Code. To qualify as a regulated investment company, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. Thus, income from the Portfolio’s investments in certain commodities-related investments may cause the Fund not to qualify as a regulated investment company. The Portfolio may invest up to 25% of its total assets in one or more ETPs that are QPTPs and whose principal activities are the buying and selling of commodities or options, futures, or forwards with respect to commodities. Income from QPTPs is generally qualifying income. If an ETP fails to qualify as a QPTP, the income generated from the Portfolio’s investment in the ETP may not be qualifying income. The Portfolio will only invest in such an ETP if it intends to qualify as a QPTP, but there is no guarantee that each such ETP will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of such ETPs as QPTPs. If the Fund fails to qualify as a regulated investment company, the Fund will be subject to tax, which will reduce returns to shareholders. Such a failure will also alter the treatment of distributions to shareholders. HIGH YIELD SECURITIES RISK:  Securities rated below investment grade, commonly referred to as “junk bonds,” include bonds that are rated Ba1/BB+/BB+ or below by Moody’s Investors Service, Inc., Fitch Inc., or Standard & Poor’s, Inc., respectively, or unrated securities considered to be of equivalent quality by the Adviser, and may involve greater risks than securities in higher rating categories. Such bonds are regarded as speculative in nature, involve greater risk of default by the issuing entity and may be subject to greater market fluctuations than higher rated debt securities. They are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The retail secondary market for these “junk bonds” may be less liquid than that of higher rated securities and adverse conditions could make it difficult at times to sell certain securities without taking a discount, which could be significant. High yield securities also may present greater credit risk because such securities may be issued in connection with corporate restructuring by highly leveraged issuers or may not be current in the payment of interest or principal or in default. U.S. GOVERNMENT AGENCY SECURITIES RISK:  Treasury securities are backed by the full faith and credit of the U.S. government as to the timely payment of principal and interest. Securities issued by U.S. government agencies or government-sponsored entities may not be guaranteed by the U.S. Treasury. If a government-sponsored entity is unable to meet its obligations, the performance of the Portfolio and, therefore, the Fund will be adversely impacted. PREPAYMENT RISK:  Mortgage-related securities may be paid off early if the borrower on the underlying mortgage prepays the mortgage or refinances the mortgage prior to the maturity date. If interest rates are falling, the Portfolio may have to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Portfolio’s and, therefore, the Fund’s income. MORTGAGE-BACKED SECURITIES RISK:  Mortgage-backed securities, other than Government National Mortgage Association (“GNMA”) mortgage-backed securities, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. Mortgage-backed securities tend to increase in value less than other debt securities when interest rates decline, but are subject to similar risk of decline in market value during periods of rising interest rates. Because of prepayment and extension risk, mortgage-backed securities react differently to changes in interest rates than other bonds. Small movements in interest rates (both increases and decreases) may quickly and significantly affect the value of certain mortgage-backed securities. MORTGAGE PASS-THROUGH SECURITIES RISK:  Most transactions in mortgage pass-through securities occur through standardized contracts for future delivery in which the exact mortgage pools to be delivered are not specified until a few days prior to settlement, referred to as a “to-be-announced transaction” or “TBA Transaction.” In a TBA Transaction, the buyer and seller agree upon general trade parameters such as agency, settlement date, par amount and price. Default by or bankruptcy of a counterparty to a TBA Transaction would expose the Portfolio to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA Transaction. REAL ESTATE SECTOR RISK:  Investments in real estate securities are subject to the risks of decreases in real estate values, overbuilding, increased competition and local or general economic conditions, increases in operating costs and property taxes, changes in zoning laws, casualty or condemnation losses, possible environmental liabilities, regulatory limitations on rent and fluctuations in rental income. Changes in interest rates may also affect the value of real estate securities. Certain real estate securities have a relatively small market capitalization, which may tend to increase the volatility of the market price of these securities. Real estate securities are dependent upon specialized management skills, have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers. In addition, a REIT may fail to qualify for favorable tax treatment under the Internal Revenue Code and may fail to maintain exemption from the registration requirements of the 1940 Act. MANAGEMENT RISK:  The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Adviser may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. AFFILIATED ETP RISK:  The Adviser may receive management or other fees from the ETPs (“Affiliated ETPs”) in which the Portfolio may invest, as well as a management fee for managing the Fund. It is possible that a conflict of interest among the Portfolio and the Affiliated ETPs could affect how the Adviser fulfills its fiduciary duties to the Portfolio and the Affiliated ETPs. Because the amount of the investment management fees to be retained by the Adviser may differ depending upon the Affiliated ETPs in which the Portfolio invests, there is a conflict of interest for the Adviser in selecting the Affiliated ETPs. In addition, the Adviser may have an incentive to take into account the effect on an Affiliated ETP in which the Portfolio may invest in determining whether, and under what circumstances, to purchase or sell shares in that Affiliated ETP. Although the Adviser takes steps to address the conflicts of interest, it is possible that the conflicts could impact the Portfolio and, therefore, the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not commenced operations as of the date of this Prospectus and therefore the Fund does not have a full calendar year of performance information.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not commenced operations as of the date of this Prospectus and therefore the Fund does not have a full calendar year of performance information.
SPDR SSgA Aggressive Global Allocation ETF | SPDR SSgA Aggressive Global Allocation ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets	0.35%	[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets	none	[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets	0.35%	[1]
YEAR 1	rr_ExpenseExampleYear01	$ 36
YEAR 3	rr_ExpenseExampleYear03	$ 113

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through at least October 31, 2014.

[4] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SSgA Active ETF Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
SPDR MFS Systematic Core Equity ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SPDR MFS Systematic Core Equity ETF
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The SPDR MFS Systematic Core Equity ETF’s (the “Fund”) investment objective is to seek capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund (“Shares”). This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This table and the example below reflect the expenses of both the Fund and the Portfolio (defined below) and do not reflect brokerage commissions you may pay on purchases and sales of the Fund’s Shares.
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	THE FUND’S PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests substantially all of its assets in the SSgA MFS Systematic Core Equity Portfolio (the "Portfolio"), a separate series of the SSgA Master Trust with an identical investment objective as the Fund. As a result, the Fund invests indirectly through the Portfolio. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus the amount of borrowings for investment purposes) in equity securities. Equity securities in which the Portfolio invests include common stocks, preferred stocks and securities convertible into stocks. In selecting securities for the Portfolio, Massachusetts Financial Services Company (the "Sub-Adviser" or "MFS") utilizes a bottom-up approach to buying and selling investments for the Portfolio. Investments are selected based on fundamental and quantitative analysis. MFS uses fundamental analysis of individual issuers and their potential in light of their financial condition, and market, economic, political, and regulatory conditions to identify potential investments. Factors considered may include analysis of an issuer's earnings, cash flows, competitive position, and management ability. MFS then uses quantitative models that systematically evaluate an issuer's valuation, price and earnings momentum, earnings quality, and other factors to determine which investments to buy and sell. While the Sub-Adviser may invest the Portfolio's assets in companies of any size, the Sub-Adviser generally focuses on companies with large market capitalizations. In selecting investments for the Portfolio, the Sub-Adviser is not constrained to any particular investment style. The Sub-Adviser may invest the Portfolio's assets in the stocks of companies it believes have above average earnings growth potential compared to other companies (growth companies), in the stocks of companies it believes are undervalued compared to their perceived worth (value companies), or in a combination of growth and value companies.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS OF INVESTING IN THE FUND
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund. Because the Fund invests substantially all of its assets in the Portfolio, it is subject to substantially the same risks as those associated with the direct ownership of the securities in which the Portfolio invests. EQUITY INVESTING RISK: The value of equity securities may increase or decrease as a result of market fluctuations, changes in interest rates and perceived trends in stock prices. PREFERRED SECURITIES RISK: Generally, preferred security holders (such as the Portfolio) have no voting rights with respect to the issuing company unless certain events occur. In addition, preferred securities are subordinated to bonds and other debt instruments in a company’s capital structure and therefore will be subject to greater credit risk than those debt instruments. Unlike debt securities, dividend payments on a preferred security typically must be declared by the issuer’s board of directors. An issuer’s board of directors is generally not under any obligation to pay a dividend (even if such dividends have accrued), and may suspend payment of dividends on preferred securities at any time. In the event an issuer of preferred securities experiences economic difficulties, the issuer’s preferred securities may lose substantial value due to the reduced likelihood that the issuer’s board of directors will declare a dividend and the fact that the preferred security may be subordinated to other securities of the same issuer. There is a chance that the issuer of any of the Portfolio’s holdings will default (fail to make scheduled dividend payments on the preferred security or scheduled interest payments on other obligations of the issuer not held by the Portfolio). CONVERTIBLE SECURITIES RISK: Convertible securities are bonds, debentures, notes, preferred stocks or other securities that may be converted or exchanged (by the holder or by the issuer) into shares of the underlying common stock (or cash or securities of equivalent value) at a stated exchange ratio. Convertible securities tend to be subordinate to other debt securities issued by the same issuer so such securities may not receive full repayment in the event of an issuer default. Also, issuers of convertible securities are often not as strong financially as issuers with higher credit ratings. Convertible securities generally provide yields higher than the underlying stocks, but generally lower than comparable non-convertible securities. Because of this higher yield, convertible securities generally sell at a price above their “conversion value,” which is the current market value of the stock to be received upon conversion. The difference between this conversion value and the price of convertible securities will vary over time depending on changes in the value of the underlying common stocks and interest rates. COMPANY RISK: Changes in the financial condition of a company or other issuer, changes in specific market, economic, political, regulatory, geopolitical, and other conditions that affect a particular type of investment or issuer, and changes in general market, economic, political, regulatory, geopolitical and other conditions can adversely affect the price of an investment. The price of securities of smaller, less well-known issuers can be more volatile than the price of securities of larger issuers or the market in general. GROWTH RISK: The Portfolio may emphasize a “growth” style of investing. The market values of growth stocks may be more volatile than other types of investments. The prices of growth stocks tend to reflect future expectations, and when those expectations change or are not met, share prices generally fall. The returns on “growth” securities may or may not move in tandem with the returns on other styles of investing or the overall stock market. VALUE RISK: The Portfolio may employ a “value” style of investing that emphasizes undervalued companies with characteristics for improved valuations. This style of investing is subject to the risk that the valuations never improve or that the returns on “value” equity securities are less than returns on other styles of investing or the overall stock market. LARGE CAP RISK: Returns on investments in stocks of large U.S. companies could trail the returns on investments in stocks of smaller and mid-sized companies. MANAGEMENT RISK: The Portfolio is actively managed, and therefore the Portfolio is subject to the risk that the investments selected by the Sub-Adviser’s investment strategy may not produce the intended results and may cause the Portfolio to underperform relative to its benchmark or other funds with a similar investment objective. PORTFOLIO TURNOVER RISK: The Portfolio may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Portfolio, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect the Portfolio and, therefore, the Fund’s performance.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, there are certain risks of investing in the Fund, and you could lose money on an investment in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history. Once the Fund has completed a full calendar year of operations, a bar chart and table will be included that will provide some indication of the risks of investing in the Fund by showing the variability of the Fund’s returns based on net assets and comparing the Fund’s performance to a broad based securities index.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not yet completed a full calendar year of investment operations and therefore does not have any performance history.
SPDR MFS Systematic Core Equity ETF | SPDR MFS Systematic Core Equity ETF
Risk/Return:	rr_RiskReturnAbstract
MANAGEMENT FEES	rr_ManagementFeesOverAssets		[1],[2]
DISTRIBUTION AND SERVICE (12b-1) FEES	rr_DistributionAndService12b1FeesOverAssets	none	[1],[3]
OTHER EXPENSES	rr_OtherExpensesOverAssets		[1],[4]
TOTAL ANNUAL FUND OPERATING EXPENSES	rr_ExpensesOverAssets		[1]
YEAR 1	rr_ExpenseExampleYear01
YEAR 3	rr_ExpenseExampleYear03

[1] The Fee Table and the Example reflect the fees and expenses of both the Fund and the Portfolio.

[2] The management fee paid to the Adviser is reduced by the proportional amount of the advisory fee, as well as acquired fund fees and expenses, of the Portfolio.

[3] The Fund has adopted a Distribution and Service (12b-1) Plan pursuant to which payments of up to 0.25% of average daily net assets may be made, however, the Board has determined that no such payments will be made through the next twelve (12) months of operation.

[4] Other Expenses are based on estimated amounts for the current fiscal year.