Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	SIT LARGE CAP GROWTH FUND INC
Prospectus Date	rr_ProspectusDate	Nov. 01, 2013
SIT MUTUAL FUNDS INC | Sit Small Cap Growth Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SUMMARY INFORMATION SIT SMALL CAP 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 28.36% of the average value of the portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	28.36%
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 with capitalizations at the time of purchase of up to $3.0 billion, or up to the market capitalization of the largest company included in the Russell 2000 Index measured at the end of the previous twelve months. The Russell 2000 Index measures the performance of the 2,000 smallest companies in the Russell 3000 Index (which is made up of the 3,000 largest U.S. companies based on total market capitalization). As of September 30, 2013, the market capitalization of the largest company included in the Russell 2000 Index measured at the end of the previous twelve months was $6.7 billion. The Adviser invests in domestic growth-oriented small 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, dominant 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.
Risk [Heading]	rr_RiskHeading	PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	You could lose money by investing in the Fund. The principal risks of investing in the Fund are as follows: 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. 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. 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.
Risk Lose Money [Text]	rr_RiskLoseMoney	You could lose money by investing in the Fund.
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 9/30/13 (not annualized) was 25.58%. Best Quarter: 20.02% (2Q03) Worst Quarter: -26.22% (4Q08)
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for periods ended December 31, 2012
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 Small Cap Growth Fund | Sit Small Cap 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	1.50%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.50%
1 Year	rr_ExpenseExampleYear01	$ 154
3 Years	rr_ExpenseExampleYear03	477
5 Years	rr_ExpenseExampleYear05	824
10 Years	rr_ExpenseExampleYear10	$ 1,801
2003	rr_AnnualReturn2003	34.57%
2004	rr_AnnualReturn2004	6.79%
2005	rr_AnnualReturn2005	18.52%
2006	rr_AnnualReturn2006	7.99%
2007	rr_AnnualReturn2007	20.43%
2008	rr_AnnualReturn2008	(42.96%)
2009	rr_AnnualReturn2009	33.06%
2010	rr_AnnualReturn2010	27.28%
2011	rr_AnnualReturn2011	(0.23%)
2012	rr_AnnualReturn2012	14.40%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	25.58%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2003
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	20.02%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(26.22%)
1 Year	rr_AverageAnnualReturnYear01	14.40%
5 Years	rr_AverageAnnualReturnYear05	1.97%
10 Years	rr_AverageAnnualReturnYear10	9.34%
SIT MUTUAL FUNDS INC | Sit Small Cap Growth Fund | Return after taxes on distributions | Sit Small Cap Growth Fund
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	14.41%
5 Years	rr_AverageAnnualReturnYear05	1.97%
10 Years	rr_AverageAnnualReturnYear10	9.34%
SIT MUTUAL FUNDS INC | Sit Small Cap Growth Fund | Return after taxes on distributions and sale of Fund shares | Sit Small Cap Growth Fund
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	9.36%
5 Years	rr_AverageAnnualReturnYear05	1.69%
10 Years	rr_AverageAnnualReturnYear10	8.33%
SIT MUTUAL FUNDS INC | Sit Small Cap Growth Fund | Russell 2000® Growth Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	14.59%
5 Years	rr_AverageAnnualReturnYear05	3.49%
10 Years	rr_AverageAnnualReturnYear10	9.80%