Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Prospectus Date	rr_ProspectusDate	Jun. 01, 2020
NORTHERN SMALL CAP CORE FUND
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SMALL CAP CORE FUND
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide long-term capital appreciation. Any income received is incidental to this objective.
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 Class I shares or Class K 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, 2021
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 20.96% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	20.96%
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	“Other Expenses” are based on estimated amounts for the current fiscal year.
Expenses Restated to Reflect Current [Text]	rr_ExpensesRestatedToReflectCurrent	Expenses have been restated to reflect current fees.
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 Class K shares and Class I shares of 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 Class K shares or Class I 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	In seeking long-term capital appreciation, the Fund will invest, under normal circumstances, at least 80% of its net assets in equity securities of small capitalization companies. Small capitalization companies generally are considered to be those whose market capitalization is, at the time the Fund makes an investment, within the range of the market capitalization of companies in the Russell 2000® Index. Companies whose capitalization no longer meets this definition after purchase may continue to be considered small capitalization companies. As of December 31, 2019, the market capitalization of the companies in the Russell 2000 Index was between approximately $12.2 million and $8.3 billion. The size of companies in the Russell 2000 Index changes with market conditions. In addition, changes to the composition of the Russell 2000 Index can change the market capitalization range of companies in the Russell 2000 Index. The Fund is not limited to the stocks included in the Russell 2000 Index and may invest in other stocks that meet the criteria of NTI discussed below. Using quantitative analysis (evaluation of financial data), NTI buys securities of small capitalization companies that it believes have favorable characteristics such as earnings quality and/or competitive returns on equity relative to their peers. The team may sell securities in order to maintain the desired portfolio characteristics of the Fund. In determining whether a company has favorable characteristics, NTI uses an evaluation process that includes, but is not limited to: Quantitative review of fundamental factors such as earnings metrics and capital deployment; Risk management analysis in which risk exposures are measured and managed at the security, sector and portfolio levels; and Systematic evaluations of new securities with attractive attributes and reevaluations of portfolio holdings. Many of the companies in which the Fund invests retain their earnings to finance current and future growth. These companies generally pay little or no dividends. The Fund may use derivatives such as stock index futures to equitize cash and enhance portfolio liquidity. NTI may engage in active trading, and will not consider portfolio turnover a limiting factor in making decisions for the Fund. Frank Russell Company does not endorse any of the securities in the Russell 2000 Index. It is not a sponsor of the Small Cap Core Fund and is not affiliated with the Fund in any way.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	As with any investment, you could lose all or part of your investment in the Fund, and the Fund’s performance could trail that of other investments. The Fund is subject to certain risks, including the principal risks noted below, any of which may adversely affect the Fund’s net asset value (“NAV”), total return and ability to meet its investment objective. Each risk noted below is considered a principal risk of investing in the Fund, regardless of the order in which it appears. The significance of each risk may change over time and you should review each risk factor carefully. MARKET RISK is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, volatility in the equity markets, market disruptions caused by local or regional events such as war, act of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment or other political regulatory, economic and social developments, and developments that impact specific economic sectors, industries or segments of the market. These risks may be magnified if certain events or developments adversely interrupt the global supply chain; in these and other circumstances, such risks might affect companies worldwide due to increasingly interconnected global economies and financial markets. Market risk includes the risk that a particular style of investing, such as growth or value, may underperform the market generally. SMALL CAP STOCK RISK is the risk that stocks of smaller companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent upon a small or inexperienced management group, and their securities may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk. INVESTMENT STYLE RISK is the risk that different investment styles (e.g., “growth”, “value” or “quantitative”) tend to shift in and out of favor, depending on market and economic conditions as well as investor sentiment. The Fund may outperform or underperform other funds that invest in similar asset classes but employ a different investment style. The Fund may also employ a combination of styles that impact its risk characteristics. QUANTITATIVE INVESTING RISK is the risk that the value of securities or other investments selected using quantitative analysis can perform differently from the market as a whole or from their expected performance and the Fund may realize a loss. This may be as a result of the factors used in building a multifactor quantitative model, the weights placed on each factor, the accuracy of historical data supplied by third parties, and changing sources of market returns. Whenever a model is used, there is also a risk that the model will not work as planned. 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. CYBERSECURITY RISK is the risk of an unauthorized breach and access to Fund assets, Fund or 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 or prevent Fund investors from purchasing, redeeming or exchanging shares or receiving distributions. The Fund and its investment adviser have limited ability to prevent or mitigate cybersecurity incidents affecting third party service providers, and such third-party service providers may have limited indemnification obligations to the Fund or its investment adviser. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact and cause financial losses to the Fund or its shareholders. Issuers of securities in which the Fund invests are also subject to cybersecurity risks, and the value of these securities could decline if the issuers experience cyber-attacks or other cyber-failures. LARGE SHAREHOLDER RISK is the risk that the Fund may experience adverse effects when certain large shareholders, including funds or accounts over which the Fund’s investment adviser or an affiliate of the investment adviser has investment discretion, purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions, which may occur rapidly and unexpectedly, may cause the Fund to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity and/or NAV. Such sales may also accelerate the realization 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 expenses being allocated over a smaller asset base. Large purchases of the Fund’s shares may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash or otherwise maintains a larger cash position than it ordinarily would. 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. SECTOR RISK is the risk that companies in similar businesses may be similarly affected by particular economic or market events, which may, in certain circumstances, cause the value of securities of all companies in a particular sector of the market to decrease. While the Fund may not concentrate in any one industry, the Fund may invest without limitation in a particular market sector. STOCK INDEX FUTURES RISK is the risk arising from the Fund’s use of futures and includes: the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts; the possible inability of the Fund to close a futures contract when desired; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of the Fund’s investment adviser to correctly predict the direction of securities prices, interest rates, currency exchange rates and other economic factors. Accordingly, under normal market conditions, the Fund will limit its exposure to stock index futures to 5% of the value of the portfolio. VALUATION RISK is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. Fair valuation of the Fund’s investments involves subjective judgment. The Fund’s ability to value its investments may be impacted by technological issues and/or errors by pricing services or other third-party service providers. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares. 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 below show the performance and returns of the Fund’s Shares Class. Effective July 31, 2020, Class K shares and Class I shares will replace the Shares Class. As of the date of this Prospectus, there were no Class K shares and Class I shares outstanding for the Fund. 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’s Shares Class from year to year and (B) how the average annual total returns of the Fund’s Shares Class compare to those of a broad-based securities market index. The performance of the Shares Class has not been adjusted to reflect the expenses applicable to Class K shares or Class I shares since the classes have different expense ratios than the expense ratio of the Shares Class. Excluding the effect of any fee waivers or reimbursements, the performance of Class K shares and Class I shares would have annual returns substantially similar to those of Shares Class because the classes invest in the same portfolio of securities. Returns would only differ to the extent of the differences in expenses between the classes. In addition to the Return Before Taxes, Return After Taxes is shown for the Fund’s Shares class to illustrate the effect of federal taxes on Fund returns. Effective February 17, 2010, the Fund’s investment strategy changed from an active small cap growth investment strategy to a quantitative small cap core investment style. The performance shown prior to that date represents performance of the Fund’s prior active small cap growth investment strategy. 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 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: (A) changes in the performance of the Fund’s Shares Class from year to year and (B) how the average annual total returns of the Fund’s Shares Class 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	northerntrust.com/funds
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 (SHARES CLASS)*
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	* Year-to-date total return for the three months ended March 31, 2020 is (29.37)%. For the periods shown in the bar chart above, the highest quarterly return was 15.90% in the fourth quarter of 2010, and the lowest quarterly return was (20.73)% in the third quarter of 2011.
Performance Table Heading	rr_PerformanceTableHeading	AVERAGE ANNUAL TOTAL RETURN (For the periods ended December 31, 2019)
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 One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	Returns in the table above are shown for the Shares Class. For periods after July 31, 2020, returns of Class K shares and Class I shares will be shown. After-tax returns for Class K shares and Class I shares will vary.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	Returns in the table above are shown for the Shares Class. For periods after July 31, 2020, returns of Class K shares and Class I shares will be shown. After-tax returns for Class K shares and Class I shares will vary. 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. In calculating the federal income taxes due on redemptions, capital gains taxes resulting from redemptions are subtracted from the redemption proceeds and the tax benefits from capital losses resulting from the redemptions are added to the redemption proceeds.
NORTHERN SMALL CAP CORE FUND | Class K
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.47%	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.08%	[1],[2]
Transfer Agent Fees	rr_Component1OtherExpensesOverAssets	0.04%	[1]
Service Fees	rr_Component2OtherExpensesOverAssets	none	[1]
Other Operating Expenses	rr_Component3OtherExpensesOverAssets	0.04%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.55%	[1]
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[1],[3]
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.49%	[1]
1 Year	rr_ExpenseExampleYear01	$ 50
3 Years	rr_ExpenseExampleYear03	170
5 Years	rr_ExpenseExampleYear05	301
10 Years	rr_ExpenseExampleYear10	684
NORTHERN SMALL CAP CORE FUND | Class I
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.47%	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.18%	[1],[2]
Transfer Agent Fees	rr_Component1OtherExpensesOverAssets	0.04%	[1]
Service Fees	rr_Component2OtherExpensesOverAssets	0.10%	[1]
Other Operating Expenses	rr_Component3OtherExpensesOverAssets	0.04%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.65%	[1]
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[1],[3]
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.59%	[1]
1 Year	rr_ExpenseExampleYear01	$ 60
3 Years	rr_ExpenseExampleYear03	202
5 Years	rr_ExpenseExampleYear05	356
10 Years	rr_ExpenseExampleYear10	$ 805
NORTHERN SMALL CAP CORE FUND | Shares Class
Risk/Return:	rr_RiskReturnAbstract
2010	rr_AnnualReturn2010	25.58%
2011	rr_AnnualReturn2011	(2.49%)
2012	rr_AnnualReturn2012	17.12%
2013	rr_AnnualReturn2013	38.78%
2014	rr_AnnualReturn2014	6.54%
2015	rr_AnnualReturn2015	(4.28%)
2016	rr_AnnualReturn2016	20.72%
2017	rr_AnnualReturn2017	13.03%
2018	rr_AnnualReturn2018	(10.21%)
2019	rr_AnnualReturn2019	23.27%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year-to-date total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Mar. 31, 2020
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(29.37%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2010
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	15.90%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(20.73%)
1-Year	rr_AverageAnnualReturnYear01	23.27%
5-Year	rr_AverageAnnualReturnYear05	7.65%
10-Year	rr_AverageAnnualReturnYear10	11.85%
Since Inception	rr_AverageAnnualReturnSinceInception	7.48%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 1999
NORTHERN SMALL CAP CORE FUND | Returns after taxes on distributions | Shares Class
Risk/Return:	rr_RiskReturnAbstract
1-Year	rr_AverageAnnualReturnYear01	21.53%
5-Year	rr_AverageAnnualReturnYear05	6.84%
10-Year	rr_AverageAnnualReturnYear10	11.04%
Since Inception	rr_AverageAnnualReturnSinceInception	6.72%
NORTHERN SMALL CAP CORE FUND | Returns after taxes on distributions and sale of Fund shares | Shares Class
Risk/Return:	rr_RiskReturnAbstract
1-Year	rr_AverageAnnualReturnYear01	15.02%
5-Year	rr_AverageAnnualReturnYear05	5.92%
10-Year	rr_AverageAnnualReturnYear10	9.72%
Since Inception	rr_AverageAnnualReturnSinceInception	6.03%
NORTHERN SMALL CAP CORE FUND | Russell 2000 Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1-Year	rr_AverageAnnualReturnYear01	25.52%
5-Year	rr_AverageAnnualReturnYear05	8.23%
10-Year	rr_AverageAnnualReturnYear10	11.83%
Since Inception	rr_AverageAnnualReturnSinceInception	8.39%

[1] Expenses have been restated to reflect current fees.

[2] “Other Expenses” are based on estimated amounts for the current fiscal year.

[3] 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, service fees, 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 0.49%. The “Total Annual Fund Operating Expenses After Expense Reimbursement” may be higher than the contractual limitation as a result of certain Fund expenses, including but not limited to service fees, that are not reimbursed. This contractual limitation may not be terminated before July 31, 2021 without the approval of the Board of Trustees.