Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SIT MUTUAL FUNDS INC
Prospectus Date	rr_ProspectusDate	Nov. 01, 2016
SIT MUTUAL FUNDS INC | Sit Developing Markets Growth Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SUMMARY INFORMATION SIT DEVELOPING MARKETS GROWTH FUND
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to maximize long-term capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
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)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transactions costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 28.14% of the average value of the portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	28.14%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	The total annual fund operating expenses do not correlate to the ratio of expenses to average net assets shown in the Fund's Financial Highlights, which does not include Acquired Fund Fees and Expenses.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in the Fund for the time periods indicated, that your investment has a 5% return each year, that the Fund’s operating expenses remain the same, and that you redeem all of your shares at the end of those periods. Although your actual costs and returns 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 market conditions, at least 80% of its net assets in common stocks of companies domiciled or operating in a developing market. Developing markets are those countries that: have emerging stock markets as defined by the International Finance Corporation, have low-to middle-income economies according to the World Bank, or have similar developing characteristics, for example, countries in the MSCI EM Index and Hong Kong are considered to be developing. As of September 30, 2016, the Fund held investments in Hong Kong, South Korea, Taiwan, Thailand, Brazil, Mexico, South Africa, China, Singapore, Israel, India, Indonesia, Peru, Chile, Malaysia, Japan, Netherlands, and Turkey. In selecting investments for the Fund, the Adviser begins by selecting countries or regions in which to invest. In making its selections, the Adviser considers several factors affecting the economy and equity market of foreign countries and regions, including: economic trends, earnings outlook, liquidity within the market, fiscal and monetary policy, currency exchange rate expectations, investment valuation, market sentiment, and social and political trends. After the country and regional allocations are determined, the Adviser seeks industries and sectors that appear to have strong earnings growth prospects. Within the selected industries and sectors, the Adviser invests in foreign growth-oriented companies it believes exhibit the potential for superior growth. The Adviser believes that a company's earnings growth is the primary determinant of its potential long-term return and evaluates a company's potential for above average long-term earnings and revenue growth. Several factors are considered in the Adviser's evaluation of a company, including: unique product or service, growing product demand, regional or country dominance and growing market share, management experience and capabilities, and strong financial condition. When selling equity securities for the Fund, the Adviser considers several factors, including changes in a company’s fundamentals and anticipated earnings. The Fund invests in small, medium and large sized companies. Small companies generally have capitalizations of under $3.0 billion, and large companies generally have a capitalization greater than $5 billion. The Fund may invest in securities representing underlying international securities such as sponsored American Depository Receipts, European Depository Receipts and Global Depository Receipts. In order to hedge against adverse movements in currency exchange rates, the Fund may from time to time enter into forward foreign currency exchange contracts.
Risk [Heading]	rr_RiskHeading	PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Developing Markets Risk: Investment in developing markets are subject to unique political, economic, and market risks that can cause the Fund's investments to be more volatile and less liquid than investments in developed markets. Foreign Currency Hedging Transactions Risk: If the Adviser's forecast of exchange rate movements is incorrect, the Fund may realize losses on their foreign currency transactions. In addition, the Fund's hedging transactions may prevent the Funds from realizing the benefits of a favorable change in the value of foreign currencies. Growth Style Investing Risk: Different types of stocks tend to shift into and out of favor with stock market investors depending on market and economic conditions. The Fund invests in growth style stocks. The Fund's performance may at times be better or worse than the performance of funds that focus on other types of stocks or that have a broader investment style. International Investing Risk: International investing involves risks not typically associated with investing in U.S. securities which may adversely affect the Fund's investment. These risks include currency risk, foreign securities market risk, foreign tax risk, information risk, investment restriction risk, and political and economic risks. Management Risk: A strategy used by the investment management team may not produce the intended results. Market Risk: The market value of securities may fall or fail to rise. Market risk may affect a single issuer, sector of the economy, or the market as a whole. The market value of securities may fluctuate, sometimes rapidly and unpredictably. Mid Cap Stock Risk: Stocks of mid cap stocks may be subject to more abrupt or erratic market movements than stocks of larger, more established companies. Small Cap Stock Risk: Stocks of smaller companies involve substantial risk. Prices of small cap stocks may be subject to more abrupt or erratic market movements than stocks of larger, more established companies. Additionally, for certain small cap stocks, there may also be limited liquidity, or trading opportunities at a favorable price or time.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	HISTORICAL PERFORMANCE
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The following bar chart and table provide information on the Fund’s volatility and performance. The Fund’s past performance before and after taxes is not necessarily an indication of how the Fund will perform in the future. The bar chart below is intended to provide you with an indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year. The table below compares the Fund’s performance over different time periods to that of the Fund’s benchmark index, which is a broad measure of market performance. Updated performance information is available at the Fund’s website at www.sitfunds.com or by calling 800-332-5580. After-tax returns are calculated using 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 Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart below is intended to provide you with an indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year. The table below compares the Fund’s performance over different time periods to that of the Fund’s benchmark index, which is a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-332-5580
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.sitfunds.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	Annual Total Returns for calendar years ended December 31
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The Fund’s year-to-date return as of 9/30/16 (not annualized) was 10.86%. Best Quarter: 32.98% (2Q09) Worst Quarter: -30.73% (4Q08)
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for periods ended December 31, 2015
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using 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 Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
SIT MUTUAL FUNDS INC | Sit Developing Markets Growth Fund | Sit Developing Markets Growth Fund
Risk/Return:	rr_RiskReturnAbstract
Redemption Fee (as a percentage of amount redeemed only on shares held for less than 30 days)	rr_RedemptionFeeOverRedemption	2.00%
Management Fees	rr_ManagementFeesOverAssets	2.00%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.02%	[1]
1 Year	rr_ExpenseExampleYear01	$ 207
3 Years	rr_ExpenseExampleYear03	640
5 Years	rr_ExpenseExampleYear05	1,098
10 Years	rr_ExpenseExampleYear10	$ 2,366
2006	rr_AnnualReturn2006	31.59%
2007	rr_AnnualReturn2007	40.72%
2008	rr_AnnualReturn2008	(55.26%)
2009	rr_AnnualReturn2009	73.97%
2010	rr_AnnualReturn2010	14.53%
2011	rr_AnnualReturn2011	(18.48%)
2012	rr_AnnualReturn2012	11.08%
2013	rr_AnnualReturn2013	0.59%
2014	rr_AnnualReturn2014	(7.79%)
2015	rr_AnnualReturn2015	(15.88%)
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2016
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	10.86%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	32.98%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(30.73%)
1 Year	rr_AverageAnnualReturnYear01	(15.88%)
5 Years	rr_AverageAnnualReturnYear05	(6.71%)
10 Years	rr_AverageAnnualReturnYear10	1.55%
SIT MUTUAL FUNDS INC | Sit Developing Markets Growth Fund | Return after taxes on distributions | Sit Developing Markets Growth Fund
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(16.48%)
5 Years	rr_AverageAnnualReturnYear05	(7.93%)
10 Years	rr_AverageAnnualReturnYear10	0.72%
SIT MUTUAL FUNDS INC | Sit Developing Markets Growth Fund | Return after taxes on distributions and sale of Fund shares | Sit Developing Markets Growth Fund
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(8.48%)
5 Years	rr_AverageAnnualReturnYear05	(4.48%)
10 Years	rr_AverageAnnualReturnYear10	1.56%
SIT MUTUAL FUNDS INC | Sit Developing Markets Growth Fund | MSCI Emerging Markets Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(16.96%)
5 Years	rr_AverageAnnualReturnYear05	(7.16%)
10 Years	rr_AverageAnnualReturnYear10	1.18%

[1] The total annual fund operating expenses do not correlate to the ratio of expenses to average net assets shown in the Fund's Financial Highlights, which does not include Acquired Fund Fees and Expenses. Acquired Fund Fees and Expenses represent fees and expenses incurred indirectly by the Fund as a result of its investment in shares of investment companies.