S000003467 [Member] Average Annual Total Returns

12 Months Ended

55 Months Ended

60 Months Ended

120 Months Ended

447 Months Ended

Dec. 31, 2025

Dec. 31, 2025

Dec. 31, 2025

Dec. 31, 2025

Dec. 31, 2025

Bloomberg Municipal Bond Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

Average Annual Return, Percent

^[1]

4.25%

0.80%

1.93%

Bloomberg 5-Year Municipal Bond Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

Average Annual Return, Percent

^[2]

5.03%

1.05%

2.34%

Sit Tax-Free Income Fund - Class S

Prospectus [Line Items]

Average Annual Return, Percent

4.38%

0.76%

2.36%

Performance Inception Date

Sep. 29, 1988

Sit Tax-Free Income Fund - Class S | After Taxes on Distributions

Prospectus [Line Items]

Average Annual Return, Percent

4.38%

0.76%

2.36%

Performance Inception Date

Sep. 29, 1988

Sit Tax-Free Income Fund - Class S | After Taxes on Distributions and Sales

Prospectus [Line Items]

Average Annual Return, Percent

4.12%

1.32%

2.57%

Performance Inception Date

Sep. 29, 1988

Sit Tax-Free Income Fund - Class Y

Prospectus [Line Items]

Average Annual Return, Percent

4.63%

Performance Inception Date

Jun. 01, 2021

[1]	A broad-based securities market index that represents the overall domestic debt markets.
[2]	A more narrowly-based index that reflects the market sectors in which the Fund invests.