Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Prospectus Date	rr_ProspectusDate	Jul. 31, 2013
NORTHERN MID CAP INDEX FUND
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	MID CAP INDEX FUND
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide investment results approximating the overall performance of the common stocks included in the Standard & Poor’s MidCap 400® Composite Stock Price Index (“S&P MidCap 400 Index”).
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	July 31, 2014
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER.
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual portfolio operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 9.57% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	9.57%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	The Total Annual Fund Operating Expenses and Total Annual Fund Operating Expenses After Expense Reimbursement will not correlate to the Fund’s ratio of average net assets to (1) expenses before reimbursements and credits and (2) expenses net of reimbursements and credits, respectively, included in the Fund’s Financial Highlights in the Fund’s complete Prospectus, which do not reflect indirect expenses, such as Acquired Fund Fees and Expenses.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE
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	PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund will invest substantially all (and at least 80%) of its net assets in equity securities included in the S&P MidCap 400 Index, in weightings that approximate the relative composition of securities contained in the S&P MidCap 400 Index, and in S&P MidCap 400 Index futures approved by the Commodity Futures Trading Commission. The S&P MidCap 400 Index is a capitalization-weighted index of mid cap common stocks selected by Standard & Poor's. The companies chosen for inclusion in the S&P MidCap 400 Index tend to be industry leaders within the U.S. economy as determined by Standard & Poor's® Ratings Services ("S&P"). However, companies are not selected by S&P for inclusion in the S&P MidCap 400 Index because they are expected to have superior stock price performance relative to the market in general or other stocks in particular. As of May 31, 2013, the market capitalization of the companies in the S&P MidCap 400 Index was between $543.1 million and $17.5 billion. The Fund is passively managed, which means it tries to duplicate the investment composition and performance of the S&P MidCap 400 Index by using computer programs and statistical procedures. The Fund's investment adviser will buy and sell securities in response to changes in the S&P MidCap 400 Index. Because the Fund will have fees and transaction expenses (while the S&P MidCap 400 Index has none), returns are likely to be below those of the S&P MidCap 400 Index. The Fund's investment adviser expects that, under normal circumstances, the quarterly performance of the Fund, before expenses, will track the performance of the S&P MidCap 400 Index within a 0.95 correlation coefficient. S&P does not endorse any of the securities in the S&P MidCap 400 Index. It is not a sponsor of the Mid Cap Index Fund and is not affiliated with the Fund in any way.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK is the risk that the value of equity securities owned by the Fund may decline, at times sharply and unpredictably, because of economic changes or other events that affect individual issuers or large portions of the market. MANAGEMENT RISK is the risk that a strategy used by the Fund's investment adviser may fail to produce the intended results. TRACKING RISK is the risk that the Fund's performance may vary substantially from the performance of the benchmark index it tracks as a result of share purchases and redemptions, transaction costs, expenses and other factors. MID CAP STOCK RISK is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market. As with any mutual fund, it is possible to lose money on an investment in the Fund. 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.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with any mutual fund, it is possible to lose money on an investment in the Fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	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.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
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 (A) changes in the performance of the Fund from year to year, and (B) how the average annual total returns of the Fund compare to those of a broad-based securities market index. The Fund's past performance, before and after taxes, 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 Web site at www.northernfunds.com 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 (A) changes in the performance of the Fund from year to year, and (B) how the average annual total returns of the Fund compare to those of a broad-based securities market index.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-595-9111
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.northernfunds.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance, before and after taxes, is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	CALENDAR YEAR TOTAL RETURN*
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	*Year to date total return for the six months ended June 30, 2013 is 14.47%. For the periods shown in the bar chart above, the highest quarterly return was 19.90% in the third quarter of 2009, and the lowest quarterly return was (25.72)% in the fourth quarter of 2008.
Performance Table Heading	rr_PerformanceTableHeading	AVERAGE ANNUAL TOTAL RETURN (For the periods ended December 31, 2012)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
NORTHERN MID CAP INDEX FUND | NORTHERN MID CAP INDEX FUND
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.20%
Other Expenses	rr_OtherExpensesOverAssets	0.31%
Administration Fees	rr_Component1OtherExpensesOverAssets	0.15%
Transfer Agency Fees	rr_Component2OtherExpensesOverAssets	0.10%
Other Operating Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.52%	[1]
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.36%)	[2]
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.16%	[1]
1 Year	rr_ExpenseExampleYear01	16
3 Years	rr_ExpenseExampleYear03	130
5 Years	rr_ExpenseExampleYear05	255
10 Years	rr_ExpenseExampleYear10	$ 618
2006	rr_AnnualReturn2006	10.05%
2007	rr_AnnualReturn2007	7.63%
2008	rr_AnnualReturn2008	(36.56%)
2009	rr_AnnualReturn2009	37.15%
2010	rr_AnnualReturn2010	26.26%
2011	rr_AnnualReturn2011	(2.05%)
2012	rr_AnnualReturn2012	17.76%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year to date total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	14.47%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	19.90%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(25.72%)
1-Year	rr_AverageAnnualReturnYear01	17.76%
5-Year	rr_AverageAnnualReturnYear05	4.85%
Since Inception	rr_AverageAnnualReturnSinceInception	6.92%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 22, 2005
NORTHERN MID CAP INDEX FUND | Return after taxes on distributions | NORTHERN MID CAP INDEX FUND
Risk/Return:	rr_RiskReturnAbstract
1-Year	rr_AverageAnnualReturnYear01	17.04%
5-Year	rr_AverageAnnualReturnYear05	4.35%
Since Inception	rr_AverageAnnualReturnSinceInception	6.30%
NORTHERN MID CAP INDEX FUND | Return after taxes on distributions and sale of Fund shares | NORTHERN MID CAP INDEX FUND
Risk/Return:	rr_RiskReturnAbstract
1-Year	rr_AverageAnnualReturnYear01	12.24%
5-Year	rr_AverageAnnualReturnYear05	3.98%
Since Inception	rr_AverageAnnualReturnSinceInception	5.80%
NORTHERN MID CAP INDEX FUND | S&P MidCap 400® Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1-Year	rr_AverageAnnualReturnYear01	17.88%
5-Year	rr_AverageAnnualReturnYear05	5.15%
Since Inception	rr_AverageAnnualReturnSinceInception	7.30%

[1] The Total Annual Fund Operating Expenses and Total Annual Fund Operating Expenses After Expense Reimbursement will not correlate to the Fund's ratio of average net assets to (1) expenses before reimbursements and credits and (2) expenses net of reimbursements and credits, respectively, included in the Fund's Financial Highlights in the Fund's complete Prospectus, which do not reflect indirect expenses, such as Acquired Fund Fees and Expenses.

[2] Northern Trust Investments, Inc. has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than acquired fund fees and expenses; a portion of the compensation paid to each Trustee who is not an officer, director or employee of Northern Trust Corporation or its subsidiaries; expenses related to third-party consultants engaged by the Board of Trustees of the Trust; membership dues paid to the Investment Company Institute and Mutual Fund Directors Forum; and extraordinary expenses and interest, if any) to the extent the "Total Annual Fund Operating Expenses" exceed 0.15%. This contractual limitation may not be terminated before July 31, 2014 without the approval of the Board of Trustees. Northern Trust Investments, Inc. serves as the investment adviser and administrator to the Fund. The Northern Trust Company, an affiliate of Northern Trust Investments, Inc., serves as transfer agent, custodian and sub-administrator to the Fund.