Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHERN FUNDS
Prospectus Date	rr_ProspectusDate	Feb. 25, 2013
INVESTORS VARIABLE NAV U.S. GOVERNMENT MONEY MARKET FUND
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	INVESTORS VARIABLE NAV U.S. GOVERNMENT MONEY MARKET FUND
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund is a money market fund that 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	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
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	“Other Expenses” are estimated for the current fiscal year since the Fund has not commenced operations as of the date of this Prospectus.
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	The Fund seeks to achieve its objective by investing, under normal circumstances, substantially all (and at least 80%) of its net assets in: Short-term bills, notes and other obligations issued or guaranteed by the U.S. Treasury (“Treasury Obligations”) and repurchase agreements backed by such securities; Securities guaranteed as to principal and interest by the U.S. government (“Government Obligations”) or by its agencies, instrumentalities or sponsored enterprises, and repurchase agreements backed by such securities; and Shares of other money market portfolios of regulated investment companies that i) limit investments to U.S. Treasury Obligations, Government Obligations, and related repurchase agreements, and ii) determine net asset values (“NAVs”) based on Rule 2a-7 (“Rule 2a-7”) under the Investment Company Act of 1940, as amended (the “1940 Act”). The Fund makes significant investments in securities issued by U.S. government-sponsored entities. Such securities are neither issued nor guaranteed by the U.S. Treasury. Under unusual circumstances, as when appropriate U.S. government securities and repurchase agreements backed by such securities are unavailable, the Fund may also invest in cash equivalents, including money market funds. While the Fund expects to invest predominantly in the securities listed above, it also may invest in other “Eligible Securities” as defined by the Securities and Exchange Commission. Eligible Securities include, generally, securities that either (a) have short-term debt ratings at the time of purchase in the two highest rating categories by a Nationally Recognized Statistical Rating Organization (“NRSRO”) or (b) are issued or guaranteed by, or otherwise allow a Fund to demand payment from, an issuer with those ratings. Securities that are unrated (including securities of issuers that have long-term but not short-term ratings) may be deemed to be Eligible Securities if they are determined to be of comparable quality by the Investment Adviser under the direction of the Board of Trustees. THE FUND HAS A VARIABLE NAV. UNLIKE A TRADITIONAL MONEY MARKET FUND, THE FUND WILL NOT USE THE AMORTIZED COST METHOD OF VALUATION AND DOES NOT SEEK TO MAINTAIN A STABLE SHARE PRICE OF $1.00. AS A RESULT, THE FUND’S SHARE PRICE, WHICH IS ITS NAV, WILL VARY AND REFLECT THE EFFECTS OF UNREALIZED APPRECIATION AND DEPRECIATION AND REALIZED LOSSES AND GAINS. The Fund is managed in accordance with Rule 2a-7. Rule 2a-7 imposes strict requirements on the investment quality, maturity, and diversification 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. In addition, the Fund must maintain a dollar-weighted average maturity of 60 days or less, and a dollar-weighted average life of 120 days or less, without regard to interest rate resets. The Fund also maintains certain minimum standards regarding daily and weekly liquid assets, and limitations on the purchase of illiquid holdings, as required by Rule 2a-7. During extraordinary market conditions and interest rate environments, all or any portion of the Fund’s assets may be uninvested and will therefore not generate income. The Fund may not achieve its investment objective during this time.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. 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. 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. 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. MANAGEMENT RISK is the risk that a strategy used by the investment management team may fail to produce the intended results. 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. Many U.S. government securities purchased by the Fund are not 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. MARKET RISK is the risk that the market values of fixed-income securities owned by the Fund may decline, at times sharply and unpredictably. 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. It is possible to lose money by investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	It is possible to lose money by investing in the Fund.
Risk Money Market Fund [Text]	rr_RiskMoneyMarketFund	It is possible to lose money by investing 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 performance table have been omitted because the Fund has been in operation for less than one calendar year.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The bar chart and performance table have been omitted because the Fund has been in operation for less than one calendar year.
INVESTORS VARIABLE NAV U.S. GOVERNMENT MONEY MARKET FUND | INVESTORS VARIABLE NAV 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	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.25%	[1]
Administration Fees	rr_Component1OtherExpensesOverAssets	0.10%
Transfer Agency Fees	rr_Component2OtherExpensesOverAssets	0.10%
Other Operating Expenses	rr_Component3OtherExpensesOverAssets	0.05%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.50%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.15%	[2]
Total Annual Fund Operating Expenses After Expense Reimbursement	rr_NetExpensesOverAssets	0.35%
1 Year	rr_ExpenseExampleYear01	36
3 Years	rr_ExpenseExampleYear03	145

[1] "Other Expenses" are estimated for the current fiscal year since the Fund has not commenced operations as of the date of this Prospectus.

[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 After Reimbursement" exceed 0.35%. This contractual limitation may not be terminated before July 31, 2014 without the approval of the Board of Trustees.