497

NORTHERN FUNDS

Money Market Fund

Municipal Money Market Fund

U.S. Government Money Market Fund

U.S. Government Select Money Market Fund

(the “Funds”)

On behalf of the Funds, and pursuant to Rule 497(c) under the Securities Act of 1933, as amended, attached for filing are exhibits containing interactive data format risk/return summary information. The interactive data file included as an exhibit to this filing relates to the to the Funds’ Prospectus filed with the Securities and Exchange Commission (“SEC”) on behalf of the Funds pursuant to Rule 497(c) on November 14, 2018 (SEC Accession No. 0001193125-18-325698), which is incorporated by reference into this Rule 497 Filing.

Exhibit Index

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

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Mar. 31, 2018
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Central Index Key	dei_EntityCentralIndexKey	0000916620
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Nov. 14, 2018
Document Effective Date	dei_DocumentEffectiveDate	Nov. 14, 2018
Prospectus Date	rr_ProspectusDate	Nov. 13, 2018
Entity Inv Company Type	dei_EntityInvCompanyType	N-1A

XML

NORTHERN MONEY MARKET FUND

<b>MONEY MARKET FUND </b>

<b>INVESTMENT OBJECTIVE</b>

The Fund seeks to maximize current income to the extent consistent with the preservation of capital and maintenance of liquidity by investing exclusively in high quality money market instruments.

<b>FEES AND EXPENSES OF THE FUND</b>

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

<b>Shareholder Fees</b> (fees paid directly from your investment)

Shareholder Fees	NORTHERN MONEY MARKET FUND NORTHERN MONEY MARKET FUND USD ($)
Shareholder Fees (fees paid directly from your investment)	none

<b>Annual Fund Operating Expenses</b> (expenses that you pay each year as a<br/> percentage of the value of your investment)

Annual Fund Operating Expenses	NORTHERN MONEY MARKET FUND NORTHERN MONEY MARKET FUND
Management Fees	0.33%
Other Expenses	0.10%
Transfer Agent Fees	0.02%
Other Operating Expenses	0.08%
Total Annual Fund Operating Expenses	0.43%
Expense Reimbursement	(0.08%)	[1]
Total Annual Fund Operating Expenses After Expense Reimbursement	0.35%

<b>EXAMPLE</b>

The following 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 redeem 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	1 Year	3 Years	5 Years	10 Years
NORTHERN MONEY MARKET FUND | NORTHERN MONEY MARKET FUND | USD ($)	36	130	233	534

<b>PRINCIPAL INVESTMENT STRATEGIES</b>

The Fund seeks to achieve its objective by investing in a broad range of high-quality, U.S. dollar-denominated government, bank and commercial obligations that are available in the money markets, including:

• Obligations of U.S. banks (including obligations of foreign branches of such banks);

• Obligations of foreign commercial banks;

• Commercial paper and other obligations issued or guaranteed by U.S. and foreign corporations and other issuers;

• Corporate bonds, notes, paper and other instruments that are of high-quality;

• Asset-backed securities and asset-backed commercial paper;

• Securities issued or guaranteed as to principal and interest by the U.S. government or by its agencies, instrumentalities or sponsored enterprises and custodial receipts with respect thereto;

• Securities issued or guaranteed by one or more foreign governments or political subdivisions, agencies or instrumentalities;

• Repurchase agreements; and

• Municipal securities issued or guaranteed by state or local governmental bodies.

Under normal market conditions, the Fund will invest at least 25% of its total assets in securities issued by companies in the financial services group of industries. Companies in the financial services group of industries include but are not limited to U.S. and non-U.S. companies involved in banking, mortgage, consumer or specialized finance, investment banking, securities brokerage, asset management and custody, insurance, financial investment, real estate and mortgage finance and financial conglomerates, and related asset-backed securities. The Fund may, however, for temporary defensive purposes, invest less than 25% of its total assets in the financial services industry if warranted due to adverse economic conditions or if investing less than 25% of its total assets in the financial services industry appears to be in the best interest of shareholders.

The Fund is a money market fund that seeks to maintain a stable net asset value (“NAV”) of $1.00 per share.

The Fund operates as a “retail money market fund,” as defined under Rule 2a-7 of the Investment Company Act of 1940, as amended. As a “retail money market fund” under Rule 2a-7, the Fund (1) is permitted to continue to use the amortized cost method of valuation to seek to maintain a stable NAV of $1.00 share price, and (2) the Board of Trustees (the “Board”) will be permitted to impose a “liquidity fee” on redemptions from the Fund (up to 2%) or temporarily restrict redemptions from the Fund for up to 10 business days during a 90-day period, as described in more detail under “Purchase and Sale of Fund Shares.”

The Securities and Exchange Commission (“SEC”) imposes strict requirements on the investment quality, maturity, diversification and liquidity of the Fund’s investments.

Accordingly, the Fund’s investments must have a remaining maturity of no more than 397 days and must be high quality. The Fund’s investment adviser may consider, among other things, credit, interest rate and prepayment risks as well as general market conditions when deciding whether to buy or sell investments for the Fund.

<b>PRINCIPAL RISKS</b>

ASSET-BACKED SECURITIES RISK. Asset-backed securities represent interests in pools of assets such as mortgages, automobile loans, credit card receivables and other financial assets. Asset-backed securities are subject to credit, interest rate, prepayment, extension, valuation and liquidity risk. These securities, in most cases, are not backed by the full faith and credit of the U.S. government and are subject to the risk of default on the underlying asset or loan, 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 securities.

COMMERCIAL PAPER RISK. Investments in commercial paper are subject to the risk that the issuer cannot issue enough new commercial paper to satisfy its obligations with respect to its outstanding commercial paper, also known as rollover risk. Commercial paper is also susceptible to changes in the issuer’s financial condition or credit quality. In addition, under certain circumstances commercial paper may become illiquid or may suffer from reduced liquidity. Commercial paper is generally unsecured, which increases the credit risk associated with this type of investment.

CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its yield. Changes in the credit rating of a debt security held by the Fund could have a similar effect.

CYBERSECURITY RISK is the risk of an unauthorized breach and access to fund assets, customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the investment adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact the Fund or its shareholders.

DEBT EXTENSION RISK is the risk that an issuer will exercise its right to pay principal on an obligation held by the Fund (such as an asset-backed security) later than expected. This may happen during a period of rising interest rates. Under these circumstances, the value of the obligation will decrease and the Fund will suffer from the inability to invest in higher yielding securities.

FINANCIAL SERVICES INDUSTRY RISK is the risk that, because the Fund will invest under normal market conditions at least 25% of its total assets in the financial services industry, the Fund will be subject to greater risk of loss by economic, business, political or other developments which generally affect this industry. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.

FOREIGN SECURITIES RISK is the risk that a foreign security, even if it is a U.S. dollar-denominated foreign security, could lose value as a result of political, financial and economic events in foreign countries, more or less stringent foreign securities regulations and accounting and disclosure standards or other factors. In addition, the Fund will be subject to the risk that an issuer of foreign sovereign debt or the government authorities that control the repayment of the debt may be unable or unwilling to repay the principal or interest when due.

GUARANTOR (OR CREDIT ENHANCEMENT) RISK is the risk that changes in credit quality of a U.S. or foreign bank, insurance company or other financial institution or such entity’s failure to fulfill its obligations could cause the Fund’s investments to decline in value. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund.

INCOME RISK is the risk that falling interest rates will cause the Fund’s income to decline. Income risk is generally higher for short-term debt securities.

INTEREST RATE RISK is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Securities with longer maturities tend to be more sensitive to changes in interest rates, causing them to be more volatile than securities with shorter maturities. Securities with shorter maturities tend to provide lower returns and be less volatile than securities with longer maturities. If interest rates rise, the Fund’s yield may not increase proportionately, and the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. The risks associated with increasing interest rates are heightened given that interest rates are near historic lows, but may increase in the future with unpredictable effects on the markets and the Fund’s investments. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. A low or declining interest rate environment may prevent the Fund from providing a positive yield or paying Fund expenses out of Fund assets and could lead to a decline in the Fund’s share price. Fluctuations in interest rates may also affect the liquidity of fixed income securities and instruments held by the Fund.

LARGE SHAREHOLDER TRANSACTIONS RISK is the risk that the Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity. Such sales may also accelerate the increase of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Fund’s expense ratio due to a smaller asset base. Large Fund share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would.

LIQUIDITY FEE AND REDEMPTION GATE RISK is the risk that the Fund may impose a “liquidity fee” (up to 2%) or “redemption gate” that temporarily restricts your ability to sell shares for up to 10 business days if the Fund’s liquidity falls below required minimums because of market conditions or other factors.

LIQUIDITY RISK is the risk that the Fund will not be able to pay redemption proceeds in a timely manner because of unusual market conditions, an unusually high volume of redemption requests, legal restrictions impairing its ability to sell particular securities at an advantageous market price or other reasons. Certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like and the Fund may have to lower the price, sell other securities instead or forgo an investment opportunity. In addition, less liquid securities may be more difficult to value and markets may become less liquid when there are fewer interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. Recently, dealers have generally been less willing to make markets for fixed income securities. All of these risks may increase during periods of market turmoil and could have a negative effect on the Fund’s performance.

MANAGEMENT RISK is the risk that a strategy used by the Fund’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results.

MARKET RISK is the risk that general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment could cause the value of your investment in the Fund, or its yield, to decline. The market value of the securities in which the Fund invests may go up or down in response to the prospects of particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets.

MUNICIPAL MARKET VOLATILITY RISK is the risk that the Fund may be adversely affected by the volatile municipal market. The increased presence of nontraditional participants (such as proprietary trading desks of investment banks and hedge funds) or the absence of traditional participants (such as individuals, insurance companies, banks and life insurance companies) in the municipal markets may lead to greater volatility in the markets because non-traditional participants may trade more frequently or in greater volume. The municipal market can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities. In recent years an increasing number of municipal issuers have defaulted on obligations, been downgraded or commenced insolvency proceedings. Municipalities continue to experience difficulties in the current economic and political environment.

MUNICIPAL SECURITIES RISK is the risk that municipal securities may be subject to credit/default risk, interest rate risk, liquidity risk and certain additional risks. The Fund may be more sensitive to adverse economic, business or political developments if it invests more than 25% of its assets in the debt securities of similar projects (such as those relating to education, health care, housing, transportation, and utilities), industrial development bonds, or in particular types of municipal securities (such as general obligation bonds, private activity bonds and moral obligation bonds). Municipal securities may be fully or partially backed or enhanced by the taxing authority of a local government, by the current or anticipated revenues from a specific project or specific assets, or by the credit of, or liquidity enhancement provided by, a private issuer. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the Fund’s investments in municipal securities. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund’s ability to sell its municipal obligations at attractive prices.

PREPAYMENT (OR CALL) RISK is the risk that prepayment of the underlying mortgages or other collateral of some fixed-income securities may result in a decreased rate of return and a decline in value of those securities.

STABLE NAV RISK is the risk that the Fund will not be able to maintain an NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Fund, especially at a time when the Fund needs to sell securities to meet shareholder redemption requests, could cause the value of the Fund’s shares to decrease to a price less than $1.00 per share. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure) the Fund could be subject to increased redemption activity, which could adversely affect its NAV.

U.S. GOVERNMENT SECURITIES RISK is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Certain U.S. government securities purchased by the Fund are neither issued nor guaranteed by the U.S. Treasury and, therefore, may not be backed by the full faith and credit of the United States. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future.

You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. The Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.

<b>FUND PERFORMANCE</b>

The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year.

The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.

Updated performance information for the Fund is available and may be obtained on the Fund’s website at northerntrust.com/funds or by calling 800-595-9111.

<b>CALENDAR YEAR TOTAL RETURN*</b>

* Year to date total return for the nine months ended September 30, 2018 is 1.26%. For the periods shown in the bar chart above, the highest quarterly return was 0.80% in the first quarter of 2008, and the lowest quarterly return was 0.00% in the second quarter of 2015.

<b>AVERAGE ANNUAL TOTAL RETURN </b><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns	Inception Date	1-Year	5-Year	10-Year	Since Inception
NORTHERN MONEY MARKET FUND | NORTHERN MONEY MARKET FUND	Apr. 11, 1994	0.92%	0.25%	0.33%	2.42%

The 7-day yield for the Fund as of December 31, 2017: 1.21%. For the current 7-day yield call 800-595-9111 or visit northerntrust.com/funds.

[1] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than certain excepted expenses, i.e., Acquired Fund Fees and Expenses, the compensation paid to each Independent Trustee of the Trust, expenses of third party consultants engaged by the Board of Trustees, membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum, expenses in connection with the negotiation and renewal of the revolving credit facility, extraordinary expenses and interest) to the extent the “Total Annual Fund Operating Expenses” exceed 0.35%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of the excepted expenses that are not reimbursed. This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus and may not be terminated before that time without the approval of the Board of Trustees.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Prospectus Date	rr_ProspectusDate	Nov. 13, 2018
NORTHERN MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<b>MONEY MARKET FUND </b>
Objective [Heading]	rr_ObjectiveHeading	<b>INVESTMENT OBJECTIVE</b>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to maximize current income to the extent consistent with the preservation of capital and maintenance of liquidity by investing exclusively in high quality money market instruments.
Expense [Heading]	rr_ExpenseHeading	<b>FEES AND EXPENSES OF THE FUND</b>
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.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	<b>Shareholder Fees</b> (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	<b>Annual Fund Operating Expenses</b> (expenses that you pay each year as a<br/> percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus
Expense Example [Heading]	rr_ExpenseExampleHeading	<b>EXAMPLE</b>
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following 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 redeem 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	<b>PRINCIPAL INVESTMENT STRATEGIES</b>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its objective by investing in a broad range of high-quality, U.S. dollar-denominated government, bank and commercial obligations that are available in the money markets, including: Obligations of U.S. banks (including obligations of foreign branches of such banks); Obligations of foreign commercial banks; Commercial paper and other obligations issued or guaranteed by U.S. and foreign corporations and other issuers; Corporate bonds, notes, paper and other instruments that are of high-quality; Asset-backed securities and asset-backed commercial paper; Securities issued or guaranteed as to principal and interest by the U.S. government or by its agencies, instrumentalities or sponsored enterprises and custodial receipts with respect thereto; Securities issued or guaranteed by one or more foreign governments or political subdivisions, agencies or instrumentalities; Repurchase agreements; and Municipal securities issued or guaranteed by state or local governmental bodies. Under normal market conditions, the Fund will invest at least 25% of its total assets in securities issued by companies in the financial services group of industries. Companies in the financial services group of industries include but are not limited to U.S. and non-U.S. companies involved in banking, mortgage, consumer or specialized finance, investment banking, securities brokerage, asset management and custody, insurance, financial investment, real estate and mortgage finance and financial conglomerates, and related asset-backed securities. The Fund may, however, for temporary defensive purposes, invest less than 25% of its total assets in the financial services industry if warranted due to adverse economic conditions or if investing less than 25% of its total assets in the financial services industry appears to be in the best interest of shareholders. The Fund is a money market fund that seeks to maintain a stable net asset value (“NAV”) of $1.00 per share. The Fund operates as a “retail money market fund,” as defined under Rule 2a-7 of the Investment Company Act of 1940, as amended. As a “retail money market fund” under Rule 2a-7, the Fund (1) is permitted to continue to use the amortized cost method of valuation to seek to maintain a stable NAV of $1.00 share price, and (2) the Board of Trustees (the “Board”) will be permitted to impose a “liquidity fee” on redemptions from the Fund (up to 2%) or temporarily restrict redemptions from the Fund for up to 10 business days during a 90-day period, as described in more detail under “Purchase and Sale of Fund Shares.” The Securities and Exchange Commission (“SEC”) imposes strict requirements on the investment quality, maturity, diversification and liquidity of the Fund’s investments. Accordingly, the Fund’s investments must have a remaining maturity of no more than 397 days and must be high quality. The Fund’s investment adviser may consider, among other things, credit, interest rate and prepayment risks as well as general market conditions when deciding whether to buy or sell investments for the Fund.
Risk [Heading]	rr_RiskHeading	<b>PRINCIPAL RISKS</b>
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	ASSET-BACKED SECURITIES RISK. Asset-backed securities represent interests in pools of assets such as mortgages, automobile loans, credit card receivables and other financial assets. Asset-backed securities are subject to credit, interest rate, prepayment, extension, valuation and liquidity risk. These securities, in most cases, are not backed by the full faith and credit of the U.S. government and are subject to the risk of default on the underlying asset or loan, 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 securities. COMMERCIAL PAPER RISK. Investments in commercial paper are subject to the risk that the issuer cannot issue enough new commercial paper to satisfy its obligations with respect to its outstanding commercial paper, also known as rollover risk. Commercial paper is also susceptible to changes in the issuer’s financial condition or credit quality. In addition, under certain circumstances commercial paper may become illiquid or may suffer from reduced liquidity. Commercial paper is generally unsecured, which increases the credit risk associated with this type of investment. CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its yield. Changes in the credit rating of a debt security held by the Fund could have a similar effect. CYBERSECURITY RISK is the risk of an unauthorized breach and access to fund assets, customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the investment adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact the Fund or its shareholders. DEBT EXTENSION RISK is the risk that an issuer will exercise its right to pay principal on an obligation held by the Fund (such as an asset-backed security) later than expected. This may happen during a period of rising interest rates. Under these circumstances, the value of the obligation will decrease and the Fund will suffer from the inability to invest in higher yielding securities. FINANCIAL SERVICES INDUSTRY RISK is the risk that, because the Fund will invest under normal market conditions at least 25% of its total assets in the financial services industry, the Fund will be subject to greater risk of loss by economic, business, political or other developments which generally affect this industry. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations. FOREIGN SECURITIES RISK is the risk that a foreign security, even if it is a U.S. dollar-denominated foreign security, could lose value as a result of political, financial and economic events in foreign countries, more or less stringent foreign securities regulations and accounting and disclosure standards or other factors. In addition, the Fund will be subject to the risk that an issuer of foreign sovereign debt or the government authorities that control the repayment of the debt may be unable or unwilling to repay the principal or interest when due. GUARANTOR (OR CREDIT ENHANCEMENT) RISK is the risk that changes in credit quality of a U.S. or foreign bank, insurance company or other financial institution or such entity’s failure to fulfill its obligations could cause the Fund’s investments to decline in value. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund. INCOME RISK is the risk that falling interest rates will cause the Fund’s income to decline. Income risk is generally higher for short-term debt securities. INTEREST RATE RISK is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Securities with longer maturities tend to be more sensitive to changes in interest rates, causing them to be more volatile than securities with shorter maturities. Securities with shorter maturities tend to provide lower returns and be less volatile than securities with longer maturities. If interest rates rise, the Fund’s yield may not increase proportionately, and the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. The risks associated with increasing interest rates are heightened given that interest rates are near historic lows, but may increase in the future with unpredictable effects on the markets and the Fund’s investments. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. A low or declining interest rate environment may prevent the Fund from providing a positive yield or paying Fund expenses out of Fund assets and could lead to a decline in the Fund’s share price. Fluctuations in interest rates may also affect the liquidity of fixed income securities and instruments held by the Fund. LARGE SHAREHOLDER TRANSACTIONS RISK is the risk that the Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity. Such sales may also accelerate the increase of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Fund’s expense ratio due to a smaller asset base. Large Fund share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would. LIQUIDITY FEE AND REDEMPTION GATE RISK is the risk that the Fund may impose a “liquidity fee” (up to 2%) or “redemption gate” that temporarily restricts your ability to sell shares for up to 10 business days if the Fund’s liquidity falls below required minimums because of market conditions or other factors. LIQUIDITY RISK is the risk that the Fund will not be able to pay redemption proceeds in a timely manner because of unusual market conditions, an unusually high volume of redemption requests, legal restrictions impairing its ability to sell particular securities at an advantageous market price or other reasons. Certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like and the Fund may have to lower the price, sell other securities instead or forgo an investment opportunity. In addition, less liquid securities may be more difficult to value and markets may become less liquid when there are fewer interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. Recently, dealers have generally been less willing to make markets for fixed income securities. All of these risks may increase during periods of market turmoil and could have a negative effect on the Fund’s performance. MANAGEMENT RISK is the risk that a strategy used by the Fund’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results. MARKET RISK is the risk that general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment could cause the value of your investment in the Fund, or its yield, to decline. The market value of the securities in which the Fund invests may go up or down in response to the prospects of particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets. MUNICIPAL MARKET VOLATILITY RISK is the risk that the Fund may be adversely affected by the volatile municipal market. The increased presence of nontraditional participants (such as proprietary trading desks of investment banks and hedge funds) or the absence of traditional participants (such as individuals, insurance companies, banks and life insurance companies) in the municipal markets may lead to greater volatility in the markets because non-traditional participants may trade more frequently or in greater volume. The municipal market can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities. In recent years an increasing number of municipal issuers have defaulted on obligations, been downgraded or commenced insolvency proceedings. Municipalities continue to experience difficulties in the current economic and political environment. MUNICIPAL SECURITIES RISK is the risk that municipal securities may be subject to credit/default risk, interest rate risk, liquidity risk and certain additional risks. The Fund may be more sensitive to adverse economic, business or political developments if it invests more than 25% of its assets in the debt securities of similar projects (such as those relating to education, health care, housing, transportation, and utilities), industrial development bonds, or in particular types of municipal securities (such as general obligation bonds, private activity bonds and moral obligation bonds). Municipal securities may be fully or partially backed or enhanced by the taxing authority of a local government, by the current or anticipated revenues from a specific project or specific assets, or by the credit of, or liquidity enhancement provided by, a private issuer. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the Fund’s investments in municipal securities. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund’s ability to sell its municipal obligations at attractive prices. PREPAYMENT (OR CALL) RISK is the risk that prepayment of the underlying mortgages or other collateral of some fixed-income securities may result in a decreased rate of return and a decline in value of those securities. STABLE NAV RISK is the risk that the Fund will not be able to maintain an NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Fund, especially at a time when the Fund needs to sell securities to meet shareholder redemption requests, could cause the value of the Fund’s shares to decrease to a price less than $1.00 per share. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure) the Fund could be subject to increased redemption activity, which could adversely affect its NAV. U.S. GOVERNMENT SECURITIES RISK is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Certain U.S. government securities purchased by the Fund are neither issued nor guaranteed by the U.S. Treasury and, therefore, may not be backed by the full faith and credit of the United States. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future. You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. The Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.
Risk Lose Money [Text]	rr_RiskLoseMoney	<b>You could lose money by investing in the Fund.</b>
Risk Money Market Fund May Not Preserve Dollar [Text]	rr_RiskMoneyMarketFundMayNotPreserveDollar	<b>Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. </b>
Risk Money Market Fund May Impose Fees or Suspend Sales [Text]	rr_RiskMoneyMarketFundMayImposeFeesOrSuspendSales	<b>The Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors.</b>
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	<b>An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. </b>
Risk Money Market Fund Sponsor May Not Provide Support [Text]	rr_RiskMoneyMarketFundSponsorMayNotProvideSupport	<b>The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.</b>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<b>FUND PERFORMANCE</b>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year. The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future. Updated performance information for the Fund is available and may be obtained on the Fund’s website at northerntrust.com/funds or by calling 800-595-9111.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-595-9111
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	northerntrust.com/funds
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	<b>CALENDAR YEAR TOTAL RETURN*</b>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	* Year to date total return for the nine months ended September 30, 2018 is 1.26%. For the periods shown in the bar chart above, the highest quarterly return was 0.80% in the first quarter of 2008, and the lowest quarterly return was 0.00% in the second quarter of 2015.
Performance Table Heading	rr_PerformanceTableHeading	<b>AVERAGE ANNUAL TOTAL RETURN </b><br/>(For the periods ended December 31, 2017)
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	The 7-day yield for the Fund as of December 31, 2017: 1.21%. For the current 7-day yield call 800-595-9111 or visit northerntrust.com/funds.
Money Market Seven Day Yield, Caption [Text]	rr_MoneyMarketSevenDayYieldCaption	The 7-day yield for the Fund as of December 31, 2017
Money Market Seven Day Yield Phone	rr_MoneyMarketSevenDayYieldPhone	800-595-9111
NORTHERN MONEY MARKET FUND | NORTHERN MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.33%
Other Expenses	rr_OtherExpensesOverAssets	0.10%
Transfer Agent Fees	rr_Component1OtherExpensesOverAssets	0.02%
Other Operating Expenses	rr_Component2OtherExpensesOverAssets	0.08%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.43%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[1]
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.35%
1 Year	rr_ExpenseExampleYear01	$ 36
3 Years	rr_ExpenseExampleYear03	130
5 Years	rr_ExpenseExampleYear05	233
10 Years	rr_ExpenseExampleYear10	$ 534
2008	rr_AnnualReturn2008	1.89%
2009	rr_AnnualReturn2009	0.13%
2010	rr_AnnualReturn2010	0.02%
2011	rr_AnnualReturn2011	0.02%
2012	rr_AnnualReturn2012	0.01%
2013	rr_AnnualReturn2013	0.01%
2014	rr_AnnualReturn2014	0.01%
2015	rr_AnnualReturn2015	0.01%
2016	rr_AnnualReturn2016	0.31%
2017	rr_AnnualReturn2017	0.92%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year to date total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	1.26%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	0.80%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	none
1-Year	rr_AverageAnnualReturnYear01	0.92%
5-Year	rr_AverageAnnualReturnYear05	0.25%
10-Year	rr_AverageAnnualReturnYear10	0.33%
Since Inception	rr_AverageAnnualReturnSinceInception	2.42%
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 11, 1994
Money Market Seven Day Yield	rr_MoneyMarketSevenDayYield	1.21%

[1] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than certain excepted expenses, i.e., Acquired Fund Fees and Expenses, the compensation paid to each Independent Trustee of the Trust, expenses of third party consultants engaged by the Board of Trustees, membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum, expenses in connection with the negotiation and renewal of the revolving credit facility, extraordinary expenses and interest) to the extent the “Total Annual Fund Operating Expenses” exceed 0.35%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of the excepted expenses that are not reimbursed. This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus and may not be terminated before that time without the approval of the Board of Trustees.

XML

NORTHERN MUNICIPAL MONEY MARKET FUND

<b>MUNICIPAL MONEY MARKET FUND<b>

<b>INVESTMENT OBJECTIVE </b>

The Fund seeks to provide, to the extent consistent with the preservation of capital and prescribed portfolio standards, a high level of income exempt from regular federal income tax by investing primarily in municipal instruments.

<b>FEES AND EXPENSES OF THE FUND</b>

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

<b>Shareholder Fees</b> (fees paid directly from your investment)

Shareholder Fees	NORTHERN MUNICIPAL MONEY MARKET FUND NORTHERN MUNICIPAL MONEY MARKET FUND USD ($)
Shareholder Fees (fees paid directly from your investment)	none

<b>Annual Fund Operating Expenses</b> (expenses that you pay each year as a<br/>percentage of the value of your investment)

Annual Fund Operating Expenses	NORTHERN MUNICIPAL MONEY MARKET FUND NORTHERN MUNICIPAL MONEY MARKET FUND
Management Fees	0.33%
Other Expenses	0.05%
Transfer Agent Fees	0.02%
Other Operating Expenses	0.03%
Total Annual Fund Operating Expenses	0.38%
Expense Reimbursement	(0.03%)	[1]
Total Annual Fund Operating Expenses After Expense Reimbursement	0.35%

<b>EXAMPLE</b>

The following 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 redeem 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	1 Year	3 Years	5 Years	10 Years
NORTHERN MUNICIPAL MONEY MARKET FUND | NORTHERN MUNICIPAL MONEY MARKET FUND | USD ($)	36	119	210	477

<b>PRINCIPAL INVESTMENT STRATEGIES</b>

The Fund seeks to achieve its objective by investing primarily in high quality short-term municipal instruments, the interest on which is exempt from regular federal income tax. High quality instruments are those that present minimal credit risk as determined by the Fund’s investment adviser. The high level of income sought by the Fund is relative to yields currently available in the tax-exempt marketplace. Municipal instruments may include:

• Fixed, variable and floating rate notes and similar debt instruments;

• Asset-backed securities that are considered municipal instruments (such as trust certificates backed by municipal bonds);

• Tax-exempt commercial paper;

• Municipal bonds, notes, paper or other instruments; and

• Municipal bonds and notes that are guaranteed as to principal and interest or backed by the U.S. government or by its agencies, instrumentalities or sponsored enterprises.

Except in extraordinary circumstances, at least 80% of the Fund’s net assets will be invested in debt instruments that pay interest that is exempt from regular federal income tax. The Fund limits its investments in Alternative Minimum Tax (“AMT”) obligations (also known as “private activity bonds”), so that the Fund ordinarily will not invest in such obligations except during temporary defensive periods or when non-AMT obligations are unavailable. AMT obligations pay interest that may be treated as an item of tax preference to shareholders under the federal AMT. To the extent that the Fund invests in AMT obligations, a portion of the Fund’s dividends may be subject to federal income tax for shareholders subject to AMT.

The Fund is a money market fund that seeks to maintain a stable net asset value (“NAV”) of $1.00 per share.

The Fund operates as a “retail money market fund,” as defined under Rule 2a-7 of the Investment Company Act of 1940, as amended. As a “retail money market fund” under Rule 2a-7, the Fund (1) is permitted to continue to use the amortized cost method of valuation to seek to maintain a stable NAV of $1.00 share price, and (2) the Board of Trustees (the “Board”) will be permitted to impose a “liquidity fee” on redemptions from the Fund (up to 2%) or temporarily restrict redemptions from the Fund for up to 10 business days during a 90-day period, as described in more detail under “Purchase and Sale of Fund Shares.”

The Securities and Exchange Commission (“SEC”) imposes strict requirements on the investment quality, maturity, diversification and liquidity of the Fund’s investments.

Accordingly, the Fund’s investments must have a remaining maturity of no more than 397 days and must be high quality. The Fund’s investment adviser may consider, among other things, credit, interest rate and prepayment risks as well as general market conditions when deciding whether to buy or sell investments for the Fund.

<b>PRINCIPAL RISKS</b>

ASSET-BACKED SECURITIES RISK. Asset-backed securities represent interests in pools of assets such as mortgages, automobile loans, credit card receivables and other financial assets. Asset-backed securities are subject to credit, interest rate, prepayment, extension, valuation and liquidity risk. These securities, in most cases, are not backed by the full faith and credit of the U.S. government and are subject to the risk of default on the underlying asset or loan, 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 securities.

CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its yield. Changes in the credit rating of a debt security held by the Fund could have a similar effect.

CYBERSECURITY RISK is the risk of an unauthorized breach and access to fund assets, customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the investment adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact the Fund or its shareholders.

DEBT EXTENSION RISK is the risk that an issuer will exercise its right to pay principal on an obligation held by the Fund (such as an asset-backed security) later than expected. This may happen during a period of rising interest rates. Under these circumstances, the value of the obligation will decrease and the Fund will suffer from the inability to invest in higher yielding securities.

GEOGRAPHIC AND SECTOR RISK is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same state, geographic region or economic sector, an adverse economic, business or political development affecting that state, region or sector may affect the value of the Fund’s investments more than if its investments were not so concentrated in such geographic region or economic sector.

GUARANTOR (OR CREDIT ENHANCEMENT) RISK is the risk that changes in credit quality of a U.S. or foreign bank, insurance company or other financial institution or such entity’s failure to fulfill its obligations could cause the Fund’s investments to decline in value. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund.

INCOME RISK is the risk that falling interest rates will cause the Fund’s income to decline. Income risk is generally higher for short-term debt securities.

INTEREST RATE RISK is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Securities with longer maturities tend to be more sensitive to changes in interest rates, causing them to be more volatile than securities with shorter maturities. Securities with shorter maturities tend to provide lower returns and be less volatile than securities with longer maturities. If interest rates rise, the Fund’s yield may not increase proportionately, and the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. The risks associated with increasing interest rates are heightened given that interest rates are near historic lows, but may increase in the future with unpredictable effects on the markets and the Fund’s investments. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. A low or declining interest rate environment may prevent the Fund from providing a positive yield or paying Fund expenses out of Fund assets and could lead to a decline in the Fund’s share price. Fluctuations in interest rates may also affect the liquidity of fixed income securities and instruments held by the Fund.

LARGE SHAREHOLDER TRANSACTIONS RISK is the risk that the Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity. Such sales may also accelerate the increase of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Fund’s expense ratio due to a smaller asset base. Large Fund share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would.

LIQUIDITY FEE AND REDEMPTION GATE RISK is the risk that the Fund may impose a “liquidity fee” (up to 2%) or “redemption gate” that temporarily restricts your ability to sell shares for up to 10 business days if the Fund’s liquidity falls below required minimums because of market conditions or other factors.

LIQUIDITY RISK is the risk that the Fund will not be able to pay redemption proceeds in a timely manner because of unusual market conditions, an unusually high volume of redemption requests, legal restrictions impairing its ability to sell particular securities at an advantageous market price or other reasons. Certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like and the Fund may have to lower the price, sell other securities instead or forgo an investment opportunity. In addition, less liquid securities may be more difficult to value and markets may become less liquid when there are fewer interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. Recently, dealers have generally been less willing to make markets for fixed income securities. All of these risks may increase during periods of market turmoil and could have a negative effect on the Fund’s performance.

MANAGEMENT RISK is the risk that a strategy used by the Fund’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results.

MARKET RISK is the risk that general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment could cause the value of your investment in the Fund, or its yield, to decline. The market value of the securities in which the Fund invests may go up or down in response to the prospects of particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets.

MUNICIPAL MARKET VOLATILITY RISK is the risk that the Fund may be adversely affected by the volatile municipal market. The increased presence of nontraditional participants (such as proprietary trading desks of investment banks and hedge funds) or the absence of traditional participants (such as individuals, insurance companies, banks and life insurance companies) in the municipal markets may lead to greater volatility in the markets because non-traditional participants may trade more frequently or in greater volume. The municipal market can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities. In recent years an increasing number of municipal issuers have defaulted on obligations, been downgraded or commenced insolvency proceedings. Municipalities continue to experience difficulties in the current economic and political environment.

MUNICIPAL SECURITIES RISK is the risk that municipal securities may be subject to credit/default risk, interest rate risk, liquidity risk and certain additional risks. The Fund may be more sensitive to adverse economic, business or political developments if it invests more than 25% of its assets in the debt securities of similar projects (such as those relating to education, health care, housing, transportation, and utilities), industrial development bonds, or in particular types of municipal securities (such as general obligation bonds, private activity bonds and moral obligation bonds). Municipal securities may be fully or partially backed or enhanced by the taxing authority of a local government, by the current or anticipated revenues from a specific project or specific assets, or by the credit of, or liquidity enhancement provided by, a private issuer. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the Fund’s investments in municipal securities. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund’s ability to sell its municipal obligations at attractive prices.

PREPAYMENT (OR CALL) RISK is the risk that prepayment of the underlying mortgages or other collateral of some fixed-income securities may result in a decreased rate of return and a decline in value of those securities.

STABLE NAV RISK is the risk that the Fund will not be able to maintain an NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Fund, especially at a time when the Fund needs to sell securities to meet shareholder redemption requests, could cause the value of the Fund’s shares to decrease to a price less than $1.00 per share. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure) the Fund could be subject to increased redemption activity, which could adversely affect its NAV.

TAX RISK is the risk that future legislative or administrative changes, court decisions or noncompliant conduct by issuers may materially affect the value of municipal instruments, the ability of the Fund to pay tax-exempt dividends, or may otherwise prevent the Fund from realizing the full current benefit of the tax-exempt status of such securities. Any such change could affect the value of an investment in the Fund.

VARIABLE OR FLOATING RATE INSTRUMENTS RISK is the risk that securities with variable or floating rates can be less sensitive to interest rate changes than securities with fixed interest rates, but may decline in value and negatively impact the Fund, particularly if changes in prevailing interest rates are more frequent or sudden than the rate changes for the variable or floating rate securities, which only occur periodically. Although variable and floating rate securities are less sensitive to interest rate risk than fixed-rate securities, they are subject to credit risk and default risk, which could impede their value.

You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. The Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.

<b>FUND PERFORMANCE</b>

The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year.

The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.

Updated performance information for the Fund is available and may be obtained on the Fund’s website at northerntrust.com/funds or by calling 800-595-9111.

<b>CALENDAR YEAR TOTAL RETURN*</b>

* Year to date total return for the nine months ended September 30, 2018 is 0.73%. For the periods shown in the bar chart above, the highest quarterly return was 0.54% in the first quarter of 2008, and the lowest quarterly return was 0.00% in the third quarter of 2015.

<b>AVERAGE ANNUAL TOTAL RETURN </b><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns	Inception Date	1-Year	5-Year	10-Year	Since Inception
NORTHERN MUNICIPAL MONEY MARKET FUND | NORTHERN MUNICIPAL MONEY MARKET FUND	Apr. 11, 1994	0.73%	0.23%	0.31%	1.58%

The 7-day yield for the Fund as of December 31, 2017: 1.25%. For the current 7-day yield call 800-595-9111 or visit northerntrust.com/funds.

[1] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than certain excepted expenses, i.e., Acquired Fund Fees and Expenses, the compensation paid to each Independent Trustee of the Trust, expenses of third party consultants engaged by the Board of Trustees, membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum, expenses in connection with the negotiation and renewal of the revolving credit facility, extraordinary expenses and interest) to the extent the “Total Annual Fund Operating Expenses” exceed 0.35%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of the excepted expenses that are not reimbursed. This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus and may not be terminated before that time without the approval of the Board of Trustees.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Prospectus Date	rr_ProspectusDate	Nov. 13, 2018
NORTHERN MUNICIPAL MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<b>MUNICIPAL MONEY MARKET FUND<b>
Objective [Heading]	rr_ObjectiveHeading	<b>INVESTMENT OBJECTIVE </b>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide, to the extent consistent with the preservation of capital and prescribed portfolio standards, a high level of income exempt from regular federal income tax by investing primarily in municipal instruments.
Expense [Heading]	rr_ExpenseHeading	<b>FEES AND EXPENSES OF THE FUND</b>
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.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	<b>Shareholder Fees</b> (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	<b>Annual Fund Operating Expenses</b> (expenses that you pay each year as a<br/>percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus
Expense Example [Heading]	rr_ExpenseExampleHeading	<b>EXAMPLE</b>
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following 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 redeem 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	<b>PRINCIPAL INVESTMENT STRATEGIES</b>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its objective by investing primarily in high quality short-term municipal instruments, the interest on which is exempt from regular federal income tax. High quality instruments are those that present minimal credit risk as determined by the Fund’s investment adviser. The high level of income sought by the Fund is relative to yields currently available in the tax-exempt marketplace. Municipal instruments may include: Fixed, variable and floating rate notes and similar debt instruments; Asset-backed securities that are considered municipal instruments (such as trust certificates backed by municipal bonds); Tax-exempt commercial paper; Municipal bonds, notes, paper or other instruments; and Municipal bonds and notes that are guaranteed as to principal and interest or backed by the U.S. government or by its agencies, instrumentalities or sponsored enterprises. Except in extraordinary circumstances, at least 80% of the Fund’s net assets will be invested in debt instruments that pay interest that is exempt from regular federal income tax. The Fund limits its investments in Alternative Minimum Tax (“AMT”) obligations (also known as “private activity bonds”), so that the Fund ordinarily will not invest in such obligations except during temporary defensive periods or when non-AMT obligations are unavailable. AMT obligations pay interest that may be treated as an item of tax preference to shareholders under the federal AMT. To the extent that the Fund invests in AMT obligations, a portion of the Fund’s dividends may be subject to federal income tax for shareholders subject to AMT. The Fund is a money market fund that seeks to maintain a stable net asset value (“NAV”) of $1.00 per share. The Fund operates as a “retail money market fund,” as defined under Rule 2a-7 of the Investment Company Act of 1940, as amended. As a “retail money market fund” under Rule 2a-7, the Fund (1) is permitted to continue to use the amortized cost method of valuation to seek to maintain a stable NAV of $1.00 share price, and (2) the Board of Trustees (the “Board”) will be permitted to impose a “liquidity fee” on redemptions from the Fund (up to 2%) or temporarily restrict redemptions from the Fund for up to 10 business days during a 90-day period, as described in more detail under “Purchase and Sale of Fund Shares.” The Securities and Exchange Commission (“SEC”) imposes strict requirements on the investment quality, maturity, diversification and liquidity of the Fund’s investments. Accordingly, the Fund’s investments must have a remaining maturity of no more than 397 days and must be high quality. The Fund’s investment adviser may consider, among other things, credit, interest rate and prepayment risks as well as general market conditions when deciding whether to buy or sell investments for the Fund.
Risk [Heading]	rr_RiskHeading	<b>PRINCIPAL RISKS</b>
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	ASSET-BACKED SECURITIES RISK. Asset-backed securities represent interests in pools of assets such as mortgages, automobile loans, credit card receivables and other financial assets. Asset-backed securities are subject to credit, interest rate, prepayment, extension, valuation and liquidity risk. These securities, in most cases, are not backed by the full faith and credit of the U.S. government and are subject to the risk of default on the underlying asset or loan, 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 securities. CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its yield. Changes in the credit rating of a debt security held by the Fund could have a similar effect. CYBERSECURITY RISK is the risk of an unauthorized breach and access to fund assets, customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the investment adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact the Fund or its shareholders. DEBT EXTENSION RISK is the risk that an issuer will exercise its right to pay principal on an obligation held by the Fund (such as an asset-backed security) later than expected. This may happen during a period of rising interest rates. Under these circumstances, the value of the obligation will decrease and the Fund will suffer from the inability to invest in higher yielding securities. GEOGRAPHIC AND SECTOR RISK is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same state, geographic region or economic sector, an adverse economic, business or political development affecting that state, region or sector may affect the value of the Fund’s investments more than if its investments were not so concentrated in such geographic region or economic sector. GUARANTOR (OR CREDIT ENHANCEMENT) RISK is the risk that changes in credit quality of a U.S. or foreign bank, insurance company or other financial institution or such entity’s failure to fulfill its obligations could cause the Fund’s investments to decline in value. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund. INCOME RISK is the risk that falling interest rates will cause the Fund’s income to decline. Income risk is generally higher for short-term debt securities. INTEREST RATE RISK is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Securities with longer maturities tend to be more sensitive to changes in interest rates, causing them to be more volatile than securities with shorter maturities. Securities with shorter maturities tend to provide lower returns and be less volatile than securities with longer maturities. If interest rates rise, the Fund’s yield may not increase proportionately, and the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. The risks associated with increasing interest rates are heightened given that interest rates are near historic lows, but may increase in the future with unpredictable effects on the markets and the Fund’s investments. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. A low or declining interest rate environment may prevent the Fund from providing a positive yield or paying Fund expenses out of Fund assets and could lead to a decline in the Fund’s share price. Fluctuations in interest rates may also affect the liquidity of fixed income securities and instruments held by the Fund. LARGE SHAREHOLDER TRANSACTIONS RISK is the risk that the Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity. Such sales may also accelerate the increase of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Fund’s expense ratio due to a smaller asset base. Large Fund share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would. LIQUIDITY FEE AND REDEMPTION GATE RISK is the risk that the Fund may impose a “liquidity fee” (up to 2%) or “redemption gate” that temporarily restricts your ability to sell shares for up to 10 business days if the Fund’s liquidity falls below required minimums because of market conditions or other factors. LIQUIDITY RISK is the risk that the Fund will not be able to pay redemption proceeds in a timely manner because of unusual market conditions, an unusually high volume of redemption requests, legal restrictions impairing its ability to sell particular securities at an advantageous market price or other reasons. Certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like and the Fund may have to lower the price, sell other securities instead or forgo an investment opportunity. In addition, less liquid securities may be more difficult to value and markets may become less liquid when there are fewer interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. Recently, dealers have generally been less willing to make markets for fixed income securities. All of these risks may increase during periods of market turmoil and could have a negative effect on the Fund’s performance. MANAGEMENT RISK is the risk that a strategy used by the Fund’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results. MARKET RISK is the risk that general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment could cause the value of your investment in the Fund, or its yield, to decline. The market value of the securities in which the Fund invests may go up or down in response to the prospects of particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets. MUNICIPAL MARKET VOLATILITY RISK is the risk that the Fund may be adversely affected by the volatile municipal market. The increased presence of nontraditional participants (such as proprietary trading desks of investment banks and hedge funds) or the absence of traditional participants (such as individuals, insurance companies, banks and life insurance companies) in the municipal markets may lead to greater volatility in the markets because non-traditional participants may trade more frequently or in greater volume. The municipal market can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities. In recent years an increasing number of municipal issuers have defaulted on obligations, been downgraded or commenced insolvency proceedings. Municipalities continue to experience difficulties in the current economic and political environment. MUNICIPAL SECURITIES RISK is the risk that municipal securities may be subject to credit/default risk, interest rate risk, liquidity risk and certain additional risks. The Fund may be more sensitive to adverse economic, business or political developments if it invests more than 25% of its assets in the debt securities of similar projects (such as those relating to education, health care, housing, transportation, and utilities), industrial development bonds, or in particular types of municipal securities (such as general obligation bonds, private activity bonds and moral obligation bonds). Municipal securities may be fully or partially backed or enhanced by the taxing authority of a local government, by the current or anticipated revenues from a specific project or specific assets, or by the credit of, or liquidity enhancement provided by, a private issuer. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the Fund’s investments in municipal securities. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund’s ability to sell its municipal obligations at attractive prices. PREPAYMENT (OR CALL) RISK is the risk that prepayment of the underlying mortgages or other collateral of some fixed-income securities may result in a decreased rate of return and a decline in value of those securities. STABLE NAV RISK is the risk that the Fund will not be able to maintain an NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Fund, especially at a time when the Fund needs to sell securities to meet shareholder redemption requests, could cause the value of the Fund’s shares to decrease to a price less than $1.00 per share. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure) the Fund could be subject to increased redemption activity, which could adversely affect its NAV. TAX RISK is the risk that future legislative or administrative changes, court decisions or noncompliant conduct by issuers may materially affect the value of municipal instruments, the ability of the Fund to pay tax-exempt dividends, or may otherwise prevent the Fund from realizing the full current benefit of the tax-exempt status of such securities. Any such change could affect the value of an investment in the Fund. VARIABLE OR FLOATING RATE INSTRUMENTS RISK is the risk that securities with variable or floating rates can be less sensitive to interest rate changes than securities with fixed interest rates, but may decline in value and negatively impact the Fund, particularly if changes in prevailing interest rates are more frequent or sudden than the rate changes for the variable or floating rate securities, which only occur periodically. Although variable and floating rate securities are less sensitive to interest rate risk than fixed-rate securities, they are subject to credit risk and default risk, which could impede their value. You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. The Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.
Risk Lose Money [Text]	rr_RiskLoseMoney	<b>You could lose money by investing in the Fund. </b>
Risk Money Market Fund May Not Preserve Dollar [Text]	rr_RiskMoneyMarketFundMayNotPreserveDollar	<b>Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so.</b>
Risk Money Market Fund May Impose Fees or Suspend Sales [Text]	rr_RiskMoneyMarketFundMayImposeFeesOrSuspendSales	<b>The Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors.</b>
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	<b>An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank.</b>
Risk Money Market Fund Sponsor May Not Provide Support [Text]	rr_RiskMoneyMarketFundSponsorMayNotProvideSupport	<b>The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.</b>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<b>FUND PERFORMANCE</b>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year. The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future. Updated performance information for the Fund is available and may be obtained on the Fund’s website at northerntrust.com/funds or by calling 800-595-9111.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-595-9111
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	northerntrust.com/funds
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	<b>CALENDAR YEAR TOTAL RETURN*</b>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	* Year to date total return for the nine months ended September 30, 2018 is 0.73%. For the periods shown in the bar chart above, the highest quarterly return was 0.54% in the first quarter of 2008, and the lowest quarterly return was 0.00% in the third quarter of 2015.
Performance Table Heading	rr_PerformanceTableHeading	<b>AVERAGE ANNUAL TOTAL RETURN </b><br/>(For the periods ended December 31, 2017)
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	The 7-day yield for the Fund as of December 31, 2017: 1.25%. For the current 7-day yield call 800-595-9111 or visit northerntrust.com/funds.
Money Market Seven Day Yield, Caption [Text]	rr_MoneyMarketSevenDayYieldCaption	The 7-day yield for the Fund as of December 31, 2017
Money Market Seven Day Yield Phone	rr_MoneyMarketSevenDayYieldPhone	800-595-9111
NORTHERN MUNICIPAL MONEY MARKET FUND | NORTHERN MUNICIPAL MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.33%
Other Expenses	rr_OtherExpensesOverAssets	0.05%
Transfer Agent Fees	rr_Component1OtherExpensesOverAssets	0.02%
Other Operating Expenses	rr_Component2OtherExpensesOverAssets	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.38%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[1]
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.35%
1 Year	rr_ExpenseExampleYear01	$ 36
3 Years	rr_ExpenseExampleYear03	119
5 Years	rr_ExpenseExampleYear05	210
10 Years	rr_ExpenseExampleYear10	$ 477
2008	rr_AnnualReturn2008	1.73%
2009	rr_AnnualReturn2009	0.16%
2010	rr_AnnualReturn2010	0.02%
2011	rr_AnnualReturn2011	0.02%
2012	rr_AnnualReturn2012	0.01%
2013	rr_AnnualReturn2013	0.02%
2014	rr_AnnualReturn2014	0.02%
2015	rr_AnnualReturn2015	0.02%
2016	rr_AnnualReturn2016	0.38%
2017	rr_AnnualReturn2017	0.73%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year to date total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	0.73%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	0.54%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	none
1-Year	rr_AverageAnnualReturnYear01	0.73%
5-Year	rr_AverageAnnualReturnYear05	0.23%
10-Year	rr_AverageAnnualReturnYear10	0.31%
Since Inception	rr_AverageAnnualReturnSinceInception	1.58%
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 11, 1994
Money Market Seven Day Yield	rr_MoneyMarketSevenDayYield	1.25%

[1] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than certain excepted expenses, i.e., Acquired Fund Fees and Expenses, the compensation paid to each Independent Trustee of the Trust, expenses of third party consultants engaged by the Board of Trustees, membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum, expenses in connection with the negotiation and renewal of the revolving credit facility, extraordinary expenses and interest) to the extent the “Total Annual Fund Operating Expenses” exceed 0.35%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of the excepted expenses that are not reimbursed. This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus and may not be terminated before that time without the approval of the Board of Trustees.

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NORTHERN U.S. GOVERNMENT MONEY MARKET FUND

<b>U.S. GOVERNMENT MONEY MARKET FUND</b>

<b>INVESTMENT OBJECTIVE </b>

The Fund seeks to maximize current income to the extent consistent with the preservation of capital and maintenance of liquidity by investing exclusively in high quality money market instruments.

<b>FEES AND EXPENSES OF THE FUND</b>

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

<b>Shareholder Fees</b> (fees paid directly from your investment)

Shareholder Fees	NORTHERN U.S. GOVERNMENT MONEY MARKET FUND NORTHERN U.S. GOVERNMENT MONEY MARKET FUND USD ($)
Shareholder Fees (fees paid directly from your investment)	none

<b>Annual Fund Operating Expenses </b> (expenses that you pay each year as a<br/> percentage of the value of your investment)

Annual Fund Operating Expenses	NORTHERN U.S. GOVERNMENT MONEY MARKET FUND NORTHERN U.S. GOVERNMENT MONEY MARKET FUND
Management Fees	0.33%
Other Expenses	0.03%
Transfer Agent Fees	0.02%
Other Operating Expenses	0.01%
Total Annual Fund Operating Expenses	0.36%
Expense Reimbursement	(0.01%)	[1]
Total Annual Fund Operating Expenses After Expense Reimbursement	0.35%

<b>EXAMPLE</b>

The following 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 redeem 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	1 Year	3 Years	5 Years	10 Years
NORTHERN U.S. GOVERNMENT MONEY MARKET FUND | NORTHERN U.S. GOVERNMENT MONEY MARKET FUND | USD ($)	36	115	201	455

<b>PRINCIPAL INVESTMENT STRATEGIES</b>

The Fund seeks to achieve its objective by investing, under normal circumstances, substantially all (and at least 99.5%) of its total assets in cash, securities issued or guaranteed as to principal and interest by the U.S. government or by a person controlled or supervised by and acting as an instrumentality of the U.S. government pursuant to authority granted by the Congress of the United States or any certificate of deposit of any of the foregoing, and repurchase agreements that are fully collateralized by cash or such securities. The Fund, under normal circumstances, will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. government securities and repurchase agreements collateralized solely by U.S. government securities.

The Fund operates as a “government money market fund” under Rule 2a-7 of the Investment Company Act of 1940, as amended. As a “government money market fund” under Rule 2a-7, the Fund (1) is permitted to use the amortized cost method of valuation to seek to maintain a stable net asset value (“NAV”) of $1.00 share price, and (2) is not required to impose a liquidity fee and/or a redemption gate on fund redemptions that might apply to other types of money market funds should certain triggering events specified in Rule 2a-7 occur.

The Securities and Exchange Commission (“SEC”) imposes strict requirements on the investment quality, maturity, diversification and liquidity of the Fund’s investments. Accordingly, the Fund’s investments must have a remaining maturity of no more than 397 days and must be high quality. The Fund’s investment adviser may consider, among other things, credit, interest rate and prepayment risks as well as general market conditions when deciding whether to buy or sell investments for the Fund.

<b>PRINCIPAL RISKS</b>

CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its yield. Changes in the credit rating of a debt security held by the Fund could have a similar effect.

CYBERSECURITY RISK is the risk of an unauthorized breach and access to fund assets, customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the investment adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact the Fund or its shareholders.

DEBT EXTENSION RISK is the risk that an issuer will exercise its right to pay principal on an obligation held by the Fund (such as an asset-backed security) later than expected. This may happen during a period of rising interest rates. Under these circumstances, the value of the obligation will decrease and the Fund will suffer from the inability to invest in higher yielding securities.

INCOME RISK is the risk that falling interest rates will cause the Fund’s income to decline. Income risk is generally higher for short-term debt securities.

INTEREST RATE RISK is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Securities with longer maturities tend to be more sensitive to changes in interest rates, causing them to be more volatile than securities with shorter maturities. Securities with shorter maturities tend to provide lower returns and be less volatile than securities with longer maturities. If interest rates rise, the Fund’s yield may not increase proportionately, and the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. The risks associated with increasing interest rates are heightened given that interest rates are near historic lows, but are expected to increase in the future with unpredictable effects on the markets and the Fund’s investments. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. A low interest or declining rate environment may prevent the Fund from providing a positive yield or paying Fund expenses out of Fund assets and could lead to a decline in the Fund’s share price. Fluctuations in interest rates may also affect the liquidity of fixed income securities and instruments held by the Fund.

LARGE SHAREHOLDER TRANSACTIONS RISK is the risk that the Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity. Such sales may also accelerate the increase of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Fund’s expense ratio due to a smaller asset base. Large Fund share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would.

MANAGEMENT RISK is the risk that a strategy used by the Fund’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results.

MARKET RISK is the risk that general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment could cause the value of your investment in the Fund, or its yield, to decline. The market value of the securities in which the Fund invests may go up or down in response to the prospects of particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets.

PREPAYMENT (OR CALL) RISK is the risk that prepayment of the underlying mortgages or other collateral of some fixed-income securities may result in a decreased rate of return and a decline in value of those securities.

STABLE NAV RISK is the risk that the Fund will not be able to maintain an NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Fund, especially at a time when the Fund needs to sell securities to meet shareholder redemption requests, could cause the value of the Fund’s shares to decrease to a price less than $1.00 per share. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure), the Fund could be subject to increased redemption activity, which could adversely affect its NAV.

U.S. GOVERNMENT SECURITIES RISK is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Certain U.S. government securities purchased by the Fund are neither issued nor guaranteed by the U.S. Treasury and, therefore, may not be backed by the full faith and credit of the United States. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future.

You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.

<b>FUND PERFORMANCE</b>

The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year.

The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.

Updated performance information for the Fund is available and may be obtained on the Fund’s website at northerntrust.com/funds or by calling 800-595-9111.

<b>CALENDAR YEAR TOTAL RETURN*</b>

* Year to date total return for the nine months ended September 30, 2018 is 1.04%. For the periods shown in the bar chart above, the highest quarterly return was 0.75% in the first quarter of 2008, and the lowest quarterly return was 0.00% in the fourth quarter of 2015.

<b>AVERAGE ANNUAL TOTAL RETURN </b><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns	Inception Date	1-Year	5-Year	10-Year	Since Inception
NORTHERN U.S. GOVERNMENT MONEY MARKET FUND | NORTHERN U.S. GOVERNMENT MONEY MARKET FUND	Apr. 11, 1994	0.57%	0.13%	0.25%	2.33%

The 7-day yield for the Fund as of December 31, 2017: 1.02%. For the current 7-day yield call 800-595-9111 or visit northerntrust.com/funds.

[1] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than certain excepted expenses, i.e., Acquired Fund Fees and Expenses, the compensation paid to each Independent Trustee of the Trust, expenses of third party consultants engaged by the Board of Trustees, membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum, expenses in connection with the negotiation and renewal of the revolving credit facility, extraordinary expenses and interest) to the extent the “Total Annual Fund Operating Expenses” exceed 0.35%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of the excepted expenses that are not reimbursed. This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus and may not be terminated before that time without the approval of the Board of Trustees.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Prospectus Date	rr_ProspectusDate	Nov. 13, 2018
NORTHERN U.S. GOVERNMENT MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<b>U.S. GOVERNMENT MONEY MARKET FUND</b>
Objective [Heading]	rr_ObjectiveHeading	<b>INVESTMENT OBJECTIVE </b>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to maximize current income to the extent consistent with the preservation of capital and maintenance of liquidity by investing exclusively in high quality money market instruments.
Expense [Heading]	rr_ExpenseHeading	<b>FEES AND EXPENSES OF THE FUND</b>
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.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	<b>Shareholder Fees</b> (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	<b>Annual Fund Operating Expenses </b> (expenses that you pay each year as a<br/> percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus
Expense Example [Heading]	rr_ExpenseExampleHeading	<b>EXAMPLE</b>
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following 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 redeem 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	<b>PRINCIPAL INVESTMENT STRATEGIES</b>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its objective by investing, under normal circumstances, substantially all (and at least 99.5%) of its total assets in cash, securities issued or guaranteed as to principal and interest by the U.S. government or by a person controlled or supervised by and acting as an instrumentality of the U.S. government pursuant to authority granted by the Congress of the United States or any certificate of deposit of any of the foregoing, and repurchase agreements that are fully collateralized by cash or such securities. The Fund, under normal circumstances, will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. government securities and repurchase agreements collateralized solely by U.S. government securities. The Fund operates as a “government money market fund” under Rule 2a-7 of the Investment Company Act of 1940, as amended. As a “government money market fund” under Rule 2a-7, the Fund (1) is permitted to use the amortized cost method of valuation to seek to maintain a stable net asset value (“NAV”) of $1.00 share price, and (2) is not required to impose a liquidity fee and/or a redemption gate on fund redemptions that might apply to other types of money market funds should certain triggering events specified in Rule 2a-7 occur. The Securities and Exchange Commission (“SEC”) imposes strict requirements on the investment quality, maturity, diversification and liquidity of the Fund’s investments. Accordingly, the Fund’s investments must have a remaining maturity of no more than 397 days and must be high quality. The Fund’s investment adviser may consider, among other things, credit, interest rate and prepayment risks as well as general market conditions when deciding whether to buy or sell investments for the Fund.
Risk [Heading]	rr_RiskHeading	<b>PRINCIPAL RISKS</b>
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its yield. Changes in the credit rating of a debt security held by the Fund could have a similar effect. CYBERSECURITY RISK is the risk of an unauthorized breach and access to fund assets, customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the investment adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact the Fund or its shareholders. DEBT EXTENSION RISK is the risk that an issuer will exercise its right to pay principal on an obligation held by the Fund (such as an asset-backed security) later than expected. This may happen during a period of rising interest rates. Under these circumstances, the value of the obligation will decrease and the Fund will suffer from the inability to invest in higher yielding securities. INCOME RISK is the risk that falling interest rates will cause the Fund’s income to decline. Income risk is generally higher for short-term debt securities. INTEREST RATE RISK is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Securities with longer maturities tend to be more sensitive to changes in interest rates, causing them to be more volatile than securities with shorter maturities. Securities with shorter maturities tend to provide lower returns and be less volatile than securities with longer maturities. If interest rates rise, the Fund’s yield may not increase proportionately, and the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. The risks associated with increasing interest rates are heightened given that interest rates are near historic lows, but are expected to increase in the future with unpredictable effects on the markets and the Fund’s investments. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. A low interest or declining rate environment may prevent the Fund from providing a positive yield or paying Fund expenses out of Fund assets and could lead to a decline in the Fund’s share price. Fluctuations in interest rates may also affect the liquidity of fixed income securities and instruments held by the Fund. LARGE SHAREHOLDER TRANSACTIONS RISK is the risk that the Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity. Such sales may also accelerate the increase of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Fund’s expense ratio due to a smaller asset base. Large Fund share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would. MANAGEMENT RISK is the risk that a strategy used by the Fund’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results. MARKET RISK is the risk that general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment could cause the value of your investment in the Fund, or its yield, to decline. The market value of the securities in which the Fund invests may go up or down in response to the prospects of particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets. PREPAYMENT (OR CALL) RISK is the risk that prepayment of the underlying mortgages or other collateral of some fixed-income securities may result in a decreased rate of return and a decline in value of those securities. STABLE NAV RISK is the risk that the Fund will not be able to maintain an NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Fund, especially at a time when the Fund needs to sell securities to meet shareholder redemption requests, could cause the value of the Fund’s shares to decrease to a price less than $1.00 per share. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure), the Fund could be subject to increased redemption activity, which could adversely affect its NAV. U.S. GOVERNMENT SECURITIES RISK is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Certain U.S. government securities purchased by the Fund are neither issued nor guaranteed by the U.S. Treasury and, therefore, may not be backed by the full faith and credit of the United States. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future. You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.
Risk Lose Money [Text]	rr_RiskLoseMoney	<b>You could lose money by investing in the Fund. </b>
Risk Money Market Fund May Not Preserve Dollar [Text]	rr_RiskMoneyMarketFundMayNotPreserveDollar	<b>Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so.</b>
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	<b>An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. </b>
Risk Money Market Fund Sponsor May Not Provide Support [Text]	rr_RiskMoneyMarketFundSponsorMayNotProvideSupport	<b>The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.</b>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<b>FUND PERFORMANCE</b>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year. The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future. Updated performance information for the Fund is available and may be obtained on the Fund’s website at northerntrust.com/funds or by calling 800-595-9111.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-595-9111
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	northerntrust.com/funds
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	<b>CALENDAR YEAR TOTAL RETURN*</b>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	* Year to date total return for the nine months ended September 30, 2018 is 1.04%. For the periods shown in the bar chart above, the highest quarterly return was 0.75% in the first quarter of 2008, and the lowest quarterly return was 0.00% in the fourth quarter of 2015.
Performance Table Heading	rr_PerformanceTableHeading	<b>AVERAGE ANNUAL TOTAL RETURN </b><br/>(For the periods ended December 31, 2017)
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	The 7-day yield for the Fund as of December 31, 2017: 1.02%. For the current 7-day yield call 800-595-9111 or visit northerntrust.com/funds.
Money Market Seven Day Yield, Caption [Text]	rr_MoneyMarketSevenDayYieldCaption	The 7-day yield for the Fund as of December 31, 2017
Money Market Seven Day Yield Phone	rr_MoneyMarketSevenDayYieldPhone	800-595-9111
NORTHERN U.S. GOVERNMENT MONEY MARKET FUND | NORTHERN U.S. GOVERNMENT MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.33%
Other Expenses	rr_OtherExpensesOverAssets	0.03%
Transfer Agent Fees	rr_Component1OtherExpensesOverAssets	0.02%
Other Operating Expenses	rr_Component2OtherExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.36%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[1]
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.35%
1 Year	rr_ExpenseExampleYear01	$ 36
3 Years	rr_ExpenseExampleYear03	115
5 Years	rr_ExpenseExampleYear05	201
10 Years	rr_ExpenseExampleYear10	$ 455
2008	rr_AnnualReturn2008	1.83%
2009	rr_AnnualReturn2009	0.03%
2010	rr_AnnualReturn2010	0.02%
2011	rr_AnnualReturn2011	0.01%
2012	rr_AnnualReturn2012	0.01%
2013	rr_AnnualReturn2013	0.01%
2014	rr_AnnualReturn2014	0.01%
2015	rr_AnnualReturn2015	0.01%
2016	rr_AnnualReturn2016	0.06%
2017	rr_AnnualReturn2017	0.57%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year to date total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	1.04%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	0.75%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	none
1-Year	rr_AverageAnnualReturnYear01	0.57%
5-Year	rr_AverageAnnualReturnYear05	0.13%
10-Year	rr_AverageAnnualReturnYear10	0.25%
Since Inception	rr_AverageAnnualReturnSinceInception	2.33%
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 11, 1994
Money Market Seven Day Yield	rr_MoneyMarketSevenDayYield	1.02%

[1] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than certain excepted expenses, i.e., Acquired Fund Fees and Expenses, the compensation paid to each Independent Trustee of the Trust, expenses of third party consultants engaged by the Board of Trustees, membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum, expenses in connection with the negotiation and renewal of the revolving credit facility, extraordinary expenses and interest) to the extent the “Total Annual Fund Operating Expenses” exceed 0.35%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of the excepted expenses that are not reimbursed. This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus and may not be terminated before that time without the approval of the Board of Trustees.

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NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND

<b>U.S. GOVERNMENT SELECT MONEY MARKET FUND</b>

<b>INVESTMENT OBJECTIVE</b>

The Fund seeks to maximize current income to the extent consistent with the preservation of capital and maintenance of liquidity by investing exclusively in high quality money market instruments.

<b>FEES AND EXPENSES OF THE FUND</b>

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

<b>Shareholder Fees</b> (fees paid directly from your investment)

Shareholder Fees	NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND USD ($)
Shareholder Fees (fees paid directly from your investment)	none

<b>Annual Fund Operating Expenses </b> (expenses that you pay each year as a<br/> percentage of the value of your investment)

Annual Fund Operating Expenses	NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND
Management Fees	0.33%
Other Expenses	0.04%
Transfer Agent Fees	0.02%
Other Operating Expenses	0.02%
Total Annual Fund Operating Expenses	0.37%
Expense Reimbursement	(0.02%)	[1]
Total Annual Fund Operating Expenses After Expense Reimbursement	0.35%

<b>EXAMPLE</b>

The following 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 redeem 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	1 Year	3 Years	5 Years	10 Years
NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND | NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND | USD ($)	36	117	206	466

<b>PRINCIPAL INVESTMENT STRATEGIES</b>

The Fund seeks to achieve its objective by investing, under normal circumstances, substantially all (and at least 99.5%) of its total assets in cash, securities issued or guaranteed as to principal and interest by the U.S. government or by a person controlled or supervised by and acting as an instrumentality of the U.S. government pursuant to authority granted by the Congress of the United States or any certificate of deposit of any of the foregoing, and repurchase agreements that are fully collateralized by cash or such securities. Subject to the foregoing 99.5% investment strategy requirement, under normal circumstances, the Fund will seek to acquire only those U.S. government securities paying interest that generally is exempt from state income taxation. The Fund, under normal circumstances, will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. government securities and repurchase agreements collateralized solely by U.S. government securities.

The Fund operates as a “government money market fund” under Rule 2a-7 of the Investment Company Act of 1940, as amended. As a “government money market fund” under Rule 2a-7, the Fund (1) is permitted to use the amortized cost method of valuation to seek to maintain a stable net asset value (“NAV”) of $1.00 share price, and (2) is not required to impose a liquidity fee and/or a redemption gate on fund redemptions that might apply to other types of money market funds should certain triggering events specified in Rule 2a-7 occur.

The Securities and Exchange Commission (“SEC”) imposes strict requirements on the investment quality, maturity, diversification and liquidity of the Fund’s investments. Accordingly, the Fund’s investments must have a remaining maturity of no more than 397 days and must be high quality. The Fund’s investment adviser may consider, among other things, credit, interest rate and prepayment risks as well as general market conditions when deciding whether to buy or sell investments for the Fund.

<b>PRINCIPAL RISKS</b>

CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its yield. Changes in the credit rating of a debt security held by the Fund could have a similar effect.

CYBERSECURITY RISK is the risk of an unauthorized breach and access to fund assets, customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the investment adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact the Fund or its shareholders.

DEBT EXTENSION RISK is the risk that an issuer will exercise its right to pay principal on an obligation held by the Fund (such as an asset-backed security) later than expected. This may happen during a period of rising interest rates. Under these circumstances, the value of the obligation will decrease and the Fund will suffer from the inability to invest in higher yielding securities.

INCOME RISK is the risk that falling interest rates will cause the Fund’s income to decline. Income risk is generally higher for short-term debt securities.

INTEREST RATE RISK is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Securities with longer maturities tend to be more sensitive to changes in interest rates, causing them to be more volatile than securities with shorter maturities. Securities with shorter maturities tend to provide lower returns and be less volatile than securities with longer maturities. If interest rates rise, the Fund’s yield may not increase proportionately, and the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. The risks associated with increasing interest rates are heightened given that interest rates are near historic lows, but are expected to increase in the future with unpredictable effects on the markets and the Fund’s investments. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. A low interest or declining rate environment may prevent the Fund from providing a positive yield or paying Fund expenses out of Fund assets and could lead to a decline in the Fund’s share price. Fluctuations in interest rates may also affect the liquidity of fixed income securities and instruments held by the Fund.

LARGE SHAREHOLDER TRANSACTIONS RISK is the risk that the Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity. Such sales may also accelerate the increase of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Fund’s expense ratio due to a smaller asset base. Large Fund share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would.

MANAGEMENT RISK is the risk that a strategy used by the Fund’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results.

MARKET RISK is the risk that general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment could cause the value of your investment in the Fund, or its yield, to decline. The market value of the securities in which the Fund invests may go up or down in response to the prospects of particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets.

PREPAYMENT (OR CALL) RISK is the risk that prepayment of the underlying mortgages or other collateral of some fixed-income securities may result in a decreased rate of return and a decline in value of those securities.

STABLE NAV RISK is the risk that the Fund will not be able to maintain an NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Fund, especially at a time when the Fund needs to sell securities to meet shareholder redemption requests, could cause the value of the Fund’s shares to decrease to a price less than $1.00 per share. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure) the Fund could be subject to increased redemption activity, which could adversely affect its NAV.

U.S. GOVERNMENT SECURITIES RISK is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Certain U.S. government securities purchased by the Fund are neither issued nor guaranteed by the U.S. Treasury and, therefore, may not be backed by the full faith and credit of the United States. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future.

You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.

<b>FUND PERFORMANCE</b>

The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year.

The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.

Updated performance information for the Fund is available and may be obtained on the Fund’s website at northerntrust.com/funds or by calling 800-595-9111.

<b>CALENDAR YEAR TOTAL RETURN*</b>

* Year to date total return for the nine months ended September 30, 2018 is 1.04%. For the periods shown in the bar chart above, the highest quarterly return was 0.71% in the first quarter of 2008, and the lowest quarterly return was 0.00% in the fourth quarter of 2015.

<b>AVERAGE ANNUAL TOTAL RETURN </b><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns	Inception Date	1-Year	5-Year	10-Year	Since Inception
NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND | NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND	Dec. 12, 1994	0.58%	0.14%	0.24%	2.26%

The 7-day yield for the Fund as of December 31, 2017: 1.00%. For the current 7-day yield call 800-595-9111 or visit northerntrust.com/funds.

[1] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than certain excepted expenses, i.e., Acquired Fund Fees and Expenses, the compensation paid to each Independent Trustee of the Trust, expenses of third party consultants engaged by the Board of Trustees, membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum, expenses in connection with the negotiation and renewal of the revolving credit facility, extraordinary expenses and interest) to the extent the “Total Annual Fund Operating Expenses” exceed 0.35%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of the excepted expenses that are not reimbursed. This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus and may not be terminated before that time without the approval of the Board of Trustees.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Prospectus Date	rr_ProspectusDate	Nov. 13, 2018
NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<b>U.S. GOVERNMENT SELECT MONEY MARKET FUND</b>
Objective [Heading]	rr_ObjectiveHeading	<b>INVESTMENT OBJECTIVE</b>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to maximize current income to the extent consistent with the preservation of capital and maintenance of liquidity by investing exclusively in high quality money market instruments.
Expense [Heading]	rr_ExpenseHeading	<b>FEES AND EXPENSES OF THE FUND</b>
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.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	<b>Shareholder Fees</b> (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	<b>Annual Fund Operating Expenses </b> (expenses that you pay each year as a<br/> percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus
Expense Example [Heading]	rr_ExpenseExampleHeading	<b>EXAMPLE</b>
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following 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 redeem 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	<b>PRINCIPAL INVESTMENT STRATEGIES</b>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its objective by investing, under normal circumstances, substantially all (and at least 99.5%) of its total assets in cash, securities issued or guaranteed as to principal and interest by the U.S. government or by a person controlled or supervised by and acting as an instrumentality of the U.S. government pursuant to authority granted by the Congress of the United States or any certificate of deposit of any of the foregoing, and repurchase agreements that are fully collateralized by cash or such securities. Subject to the foregoing 99.5% investment strategy requirement, under normal circumstances, the Fund will seek to acquire only those U.S. government securities paying interest that generally is exempt from state income taxation. The Fund, under normal circumstances, will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. government securities and repurchase agreements collateralized solely by U.S. government securities. The Fund operates as a “government money market fund” under Rule 2a-7 of the Investment Company Act of 1940, as amended. As a “government money market fund” under Rule 2a-7, the Fund (1) is permitted to use the amortized cost method of valuation to seek to maintain a stable net asset value (“NAV”) of $1.00 share price, and (2) is not required to impose a liquidity fee and/or a redemption gate on fund redemptions that might apply to other types of money market funds should certain triggering events specified in Rule 2a-7 occur. The Securities and Exchange Commission (“SEC”) imposes strict requirements on the investment quality, maturity, diversification and liquidity of the Fund’s investments. Accordingly, the Fund’s investments must have a remaining maturity of no more than 397 days and must be high quality. The Fund’s investment adviser may consider, among other things, credit, interest rate and prepayment risks as well as general market conditions when deciding whether to buy or sell investments for the Fund.
Risk [Heading]	rr_RiskHeading	<b>PRINCIPAL RISKS</b>
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its yield. Changes in the credit rating of a debt security held by the Fund could have a similar effect. CYBERSECURITY RISK is the risk of an unauthorized breach and access to fund assets, customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the investment adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact the Fund or its shareholders. DEBT EXTENSION RISK is the risk that an issuer will exercise its right to pay principal on an obligation held by the Fund (such as an asset-backed security) later than expected. This may happen during a period of rising interest rates. Under these circumstances, the value of the obligation will decrease and the Fund will suffer from the inability to invest in higher yielding securities. INCOME RISK is the risk that falling interest rates will cause the Fund’s income to decline. Income risk is generally higher for short-term debt securities. INTEREST RATE RISK is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Securities with longer maturities tend to be more sensitive to changes in interest rates, causing them to be more volatile than securities with shorter maturities. Securities with shorter maturities tend to provide lower returns and be less volatile than securities with longer maturities. If interest rates rise, the Fund’s yield may not increase proportionately, and the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. The risks associated with increasing interest rates are heightened given that interest rates are near historic lows, but are expected to increase in the future with unpredictable effects on the markets and the Fund’s investments. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. A low interest or declining rate environment may prevent the Fund from providing a positive yield or paying Fund expenses out of Fund assets and could lead to a decline in the Fund’s share price. Fluctuations in interest rates may also affect the liquidity of fixed income securities and instruments held by the Fund. LARGE SHAREHOLDER TRANSACTIONS RISK is the risk that the Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity. Such sales may also accelerate the increase of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Fund’s expense ratio due to a smaller asset base. Large Fund share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would. MANAGEMENT RISK is the risk that a strategy used by the Fund’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results. MARKET RISK is the risk that general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment could cause the value of your investment in the Fund, or its yield, to decline. The market value of the securities in which the Fund invests may go up or down in response to the prospects of particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets. PREPAYMENT (OR CALL) RISK is the risk that prepayment of the underlying mortgages or other collateral of some fixed-income securities may result in a decreased rate of return and a decline in value of those securities. STABLE NAV RISK is the risk that the Fund will not be able to maintain an NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Fund, especially at a time when the Fund needs to sell securities to meet shareholder redemption requests, could cause the value of the Fund’s shares to decrease to a price less than $1.00 per share. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure) the Fund could be subject to increased redemption activity, which could adversely affect its NAV. U.S. GOVERNMENT SECURITIES RISK is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Certain U.S. government securities purchased by the Fund are neither issued nor guaranteed by the U.S. Treasury and, therefore, may not be backed by the full faith and credit of the United States. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future. You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.
Risk Lose Money [Text]	rr_RiskLoseMoney	<b>You could lose money by investing in the Fund. </b>
Risk Money Market Fund May Not Preserve Dollar [Text]	rr_RiskMoneyMarketFundMayNotPreserveDollar	<b>Although the Fund seeks to preserve the value of your investment at $1.00 per share, the Fund cannot guarantee it will do so.</b>
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	<b>An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank.</b>
Risk Money Market Fund Sponsor May Not Provide Support [Text]	rr_RiskMoneyMarketFundSponsorMayNotProvideSupport	<b>The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.</b>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<b>FUND PERFORMANCE</b>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year. The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future. Updated performance information for the Fund is available and may be obtained on the Fund’s website at northerntrust.com/funds or by calling 800-595-9111.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and table that follow provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund from year to year.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-595-9111
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	northerntrust.com/funds
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	<b>CALENDAR YEAR TOTAL RETURN*</b>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	* Year to date total return for the nine months ended September 30, 2018 is 1.04%. For the periods shown in the bar chart above, the highest quarterly return was 0.71% in the first quarter of 2008, and the lowest quarterly return was 0.00% in the fourth quarter of 2015.
Performance Table Heading	rr_PerformanceTableHeading	<b>AVERAGE ANNUAL TOTAL RETURN </b><br/>(For the periods ended December 31, 2017)
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	The 7-day yield for the Fund as of December 31, 2017: 1.00%. For the current 7-day yield call 800-595-9111 or visit northerntrust.com/funds.
Money Market Seven Day Yield, Caption [Text]	rr_MoneyMarketSevenDayYieldCaption	The 7-day yield for the Fund as of December 31, 2017
Money Market Seven Day Yield Phone	rr_MoneyMarketSevenDayYieldPhone	800-595-9111
NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND | NORTHERN U.S. GOVERNMENT SELECT MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.33%
Other Expenses	rr_OtherExpensesOverAssets	0.04%
Transfer Agent Fees	rr_Component1OtherExpensesOverAssets	0.02%
Other Operating Expenses	rr_Component2OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.37%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[1]
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.35%
1 Year	rr_ExpenseExampleYear01	$ 36
3 Years	rr_ExpenseExampleYear03	117
5 Years	rr_ExpenseExampleYear05	206
10 Years	rr_ExpenseExampleYear10	$ 466
2008	rr_AnnualReturn2008	1.70%
2009	rr_AnnualReturn2009	0.02%
2010	rr_AnnualReturn2010	0.01%
2011	rr_AnnualReturn2011	0.01%
2012	rr_AnnualReturn2012	0.01%
2013	rr_AnnualReturn2013	0.01%
2014	rr_AnnualReturn2014	0.01%
2015	rr_AnnualReturn2015	0.01%
2016	rr_AnnualReturn2016	0.09%
2017	rr_AnnualReturn2017	0.58%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year to date total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	1.04%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	0.71%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	none
1-Year	rr_AverageAnnualReturnYear01	0.58%
5-Year	rr_AverageAnnualReturnYear05	0.14%
10-Year	rr_AverageAnnualReturnYear10	0.24%
Since Inception	rr_AverageAnnualReturnSinceInception	2.26%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 12, 1994
Money Market Seven Day Yield	rr_MoneyMarketSevenDayYield	1.00%

[1] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than certain excepted expenses, i.e., Acquired Fund Fees and Expenses, the compensation paid to each Independent Trustee of the Trust, expenses of third party consultants engaged by the Board of Trustees, membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum, expenses in connection with the negotiation and renewal of the revolving credit facility, extraordinary expenses and interest) to the extent the “Total Annual Fund Operating Expenses” exceed 0.35%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of the excepted expenses that are not reimbursed. This contractual limitation will remain in effect for at least one year from the effective date of this Prospectus and may not be terminated before that time without the approval of the Board of Trustees.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Prospectus Date	rr_ProspectusDate	Nov. 13, 2018
Document Creation Date	dei_DocumentCreationDate	Nov. 14, 2018