XML 81 R2.htm IDEA: XBRL DOCUMENT v3.24.4
Shareholder Report
 12 Months Ended
Nov. 30, 2024
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSR
Amendment Flag false
Registrant Name Northern Institutional Funds
Entity Central Index Key 0000710124
Entity Investment Company Type N-1A
Document Period End Date Nov. 30, 2024
C000003422 [Member]  
Shareholder Report [Line Items]  
Fund Name U.S. GOVERNMENT SELECT PORTFOLIO
Class Name SERVICE SHARES
Trading Symbol BSCXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the U.S. Government Select Portfolio (the “Portfolio”) for the period of December 1, 2023 to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1
U.S. GOVERNMENT SELECT PORTFOLIO
(SERVICE SHARES/BSCXX)		 $17 0.17%
​1
Reflects applicable expense reimbursements and fee waivers.
Expenses Paid, Amount $ 17 [1]
Expense Ratio, Percent 0.17% [1]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $10,000 investment in the Service Shares class of the Portfolio and compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years.
GROWTH OF $10,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns 1 year 5 years 10 years
U.S. GOVERNMENT SELECT PORTFOLIO (SERVICE SHARES/BSCXX) 5.22% 2.30% 1.60%
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 32,385,321,000
Holdings Count | Holding 122
Advisory Fees Paid, Amount $ 44,231,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $32,385,321
Total number of portfolio holdings 122
Total net advisory fees paid (in thousands) $44,231
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
Repurchase Agreements 48.9%
U.S. Government Agencies 31.9%
U.S. Government Obligations 16.2%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000003421 [Member]  
Shareholder Report [Line Items]  
Fund Name U.S. GOVERNMENT SELECT PORTFOLIO
Class Name SHARES
Trading Symbol BGSXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the U.S. Government Select Portfolio (the “Portfolio”) for the period of December 1, 2023 to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1
U.S. GOVERNMENT SELECT PORTFOLIO
(SHARES/BGSXX)		 $17 0.17%
​1
Reflects applicable expense reimbursements and fee waivers.
Expenses Paid, Amount $ 17 [2]
Expense Ratio, Percent 0.17% [2]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $5,000,000 investment in the Shares class of the Portfolio and compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years.
GROWTH OF $5,000,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns 1 year 5 years 10 years
U.S. GOVERNMENT SELECT PORTFOLIO (SHARES/BGSXX) 5.22% 2.30% 1.60%
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 32,385,321,000
Holdings Count | Holding 122
Advisory Fees Paid, Amount $ 44,231,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $32,385,321
Total number of portfolio holdings 122
Total net advisory fees paid (in thousands) $44,231
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
Repurchase Agreements 48.9%
U.S. Government Agencies 31.9%
U.S. Government Obligations 16.2%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000146024 [Member]  
Shareholder Report [Line Items]  
Fund Name U.S. GOVERNMENT SELECT PORTFOLIO
Class Name SIEBERT WILLIAMS SHANK SHARES
Trading Symbol WCGXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the U.S. Government Select Portfolio (the “Portfolio”) for the period of December 1, 2023 to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1
U.S. GOVERNMENT SELECT PORTFOLIO
(SIEBERT WILLIAMS SHANK SHARES/WCGXX)		 $17 0.17%
​1
Reflects applicable expense reimbursements and fee waivers.
Expenses Paid, Amount $ 17 [3]
Expense Ratio, Percent 0.17% [3]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $10,000 investment in the Siebert Williams Shank Shares class of the Portfolio and compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years.
GROWTH OF $10,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns 1 year 5 years 10 years
U.S. GOVERNMENT SELECT PORTFOLIO (SIEBERT WILLIAMS SHANK SHARES/WCGXX) 5.22% 2.30% 1.60%
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 32,385,321,000
Holdings Count | Holding 122
Advisory Fees Paid, Amount $ 44,231,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $32,385,321
Total number of portfolio holdings 122
Total net advisory fees paid (in thousands) $44,231
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
Repurchase Agreements 48.9%
U.S. Government Agencies 31.9%
U.S. Government Obligations 16.2%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000003449 [Member]  
Shareholder Report [Line Items]  
Fund Name U.S. GOVERNMENT PORTFOLIO
Class Name SHARES
Trading Symbol BNGXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the U.S. Government Portfolio (the “Portfolio”) for the period of December 1, 2023 to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1
U.S. GOVERNMENT PORTFOLIO
(SHARES/BNGXX)		 $26 0.25%
​1
Reflects applicable expense reimbursements and fee waivers.
Expenses Paid, Amount $ 26 [4]
Expense Ratio, Percent 0.25% [4]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $5,000,000 investment in the Shares class of the Portfolio and compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years.
GROWTH OF $5,000,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns 1 year 5 years 10 years
U.S. GOVERNMENT PORTFOLIO (SHARES/BNGXX) 5.16% 2.26% 1.56%
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 23,036,216,000
Holdings Count | Holding 120
Advisory Fees Paid, Amount $ 46,333,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $23,036,216
Total number of portfolio holdings 120
Total net advisory fees paid (in thousands) $46,333
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
Repurchase Agreements 51.0%
U.S. Government Agencies 33.5%
U.S. Government Obligations 15.0%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000003457 [Member]  
Shareholder Report [Line Items]  
Fund Name LIQUID ASSETS PORTFOLIO
Class Name LIQUID ASSETS PORTFOLIO
Trading Symbol NILAP
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the Liquid Assets Portfolio (the “Portfolio”) for the period of December 1, 2023 to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/institutional-liquid-assets-portfolio#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/institutional-liquid-assets-portfolio#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Fund (Class) Costs of a $10,000 investment1 Costs paid as a percentage of a $10,000 investment1
LIQUID ASSETS PORTFOLIO (SHARES/NILAP) $3 0.03%
​1
Reflects applicable expense reimbursements and fee waivers.
Expenses Paid, Amount $ 3 [5]
Expense Ratio, Percent 0.03% [5]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $10,000 investment in the Shares class of the Portfolio and compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years.
GROWTH OF $10,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns 1 year 5 years 10 years
LIQUID ASSETS PORTFOLIO (SHARES/NILAP) 5.41% 2.47% 1.79%
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/institutional-liquid-assets-portfolio#performance.
Net Assets $ 2,120,831,000
Holdings Count | Holding 51
Advisory Fees Paid, Amount $ 46,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $2,120,831
Total number of portfolio holdings 51
Total net advisory fees paid (in thousands) $46
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
Repurchase Agreements 66.2%
U.S. Government Agencies 18.4%
U.S. Government Obligations 16.3%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000070154 [Member]  
Shareholder Report [Line Items]  
Fund Name TREASURY PORTFOLIO
Class Name PREMIER SHARES
Trading Symbol NTPXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the Treasury Portfolio (the “Portfolio”) for the period of December 1, 2023 to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1
TREASURY PORTFOLIO
(PREMIER SHARES/NTPXX)		 $21 0.20%
​1
Reflects applicable expense reimbursements and fee waivers.
Expenses Paid, Amount $ 21 [6]
Expense Ratio, Percent 0.20% [6]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $10,000 investment in the Premier Shares class of the Portfolio at inception on August 1, 2016 and compares the initial and subsequent account values at the end of each of the completed fiscal years since inception.
GROWTH OF $10,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns 1 year 5 years Since
Inception
TREASURY PORTFOLIO (PREMIER SHARES/NTPXX) 5.18% 2.28% 1.90%
Performance Inception Date Aug. 01, 2016
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 88,102,728,000
Holdings Count | Holding 86
Advisory Fees Paid, Amount $ 104,587,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $88,102,728
Total number of portfolio holdings 86
Total net advisory fees paid (in thousands) $104,587
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
U.S. Government Obligations 49.3%
Repurchase Agreements 45.6%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000070152 [Member]  
Shareholder Report [Line Items]  
Fund Name TREASURY PORTFOLIO
Class Name SHARES
Trading Symbol NITXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the Treasury Portfolio (the “Portfolio”) for the period of December 1, 2023 to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1
TREASURY PORTFOLIO
(SHARES/NITXX)		 $15 0.15%
​1
Reflects applicable expense reimbursements and fee waivers.
Expenses Paid, Amount $ 15 [7]
Expense Ratio, Percent 0.15% [7]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $5,000,000 investment in the Shares class of the Portfolio and compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years.
GROWTH OF $5,000,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns 1 year 5 years 10 years
TREASURY PORTFOLIO (SHARES/NITXX) 5.23% 2.32% 1.63%
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 88,102,728,000
Holdings Count | Holding 86
Advisory Fees Paid, Amount $ 104,587,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $88,102,728
Total number of portfolio holdings 86
Total net advisory fees paid (in thousands) $104,587
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
U.S. Government Obligations 49.3%
Repurchase Agreements 45.6%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000232976 [Member]  
Shareholder Report [Line Items]  
Fund Name TREASURY PORTFOLIO
Class Name SIEBERT WILLIAMS SHANK SHARES
Trading Symbol SWSXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the Treasury Portfolio (the “Portfolio”) for the period of December 1, 2023 to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1
TREASURY PORTFOLIO
(SIEBERT WILLIAMS SHANK SHARES/SWSXX)		 $15 0.15%
​1
Reflects applicable expense reimbursements and fee waivers.
Expenses Paid, Amount $ 15 [8]
Expense Ratio, Percent 0.15% [8]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $10,000 investment in the Siebert Williams Shank Shares class of the Portfolio and compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years. Siebert Williams Shank Shares commenced operations on December 22, 2021. Performance of Siebert Williams Shank Shares prior to that date is for the Fund’s Shares class. Siebert Williams Shank Shares would have substantially similar annual returns because the Shares Class is invested in the same portfolio of securities and the annual returns would differ only to the extent that the classes do not have the same expenses.
GROWTH OF $10,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns 1 year 5 years 10 years
TREASURY PORTFOLIO (SIEBERT WILLIAMS SHANK SHARES/SWSXX) 5.23% 2.32% 1.63%
Performance Inception Date Dec. 22, 2021
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 88,102,728,000
Holdings Count | Holding 86
Advisory Fees Paid, Amount $ 104,587,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $88,102,728
Total number of portfolio holdings 86
Total net advisory fees paid (in thousands) $104,587
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
U.S. Government Obligations 49.3%
Repurchase Agreements 45.6%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000193058 [Member]  
Shareholder Report [Line Items]  
Fund Name TREASURY INSTRUMENTS PORTFOLIO
Class Name PREMIER SHARES
Trading Symbol NPYXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the Treasury Instruments Portfolio (the “Portfolio”) for the period of June 11, 2024 (Commencement of Class Operations) to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1,2
TREASURY INSTRUMENTS PORTFOLIO
(PREMIER SHARES/NPYXX)		 $4* 0.09%
​*
For the period from June 11, 2024 (Commencement of Class Operations) through November 30, 2024.
​1
Reflects applicable expense reimbursements and fee waivers.
​2
Expense ratio is expressed on an annualized basis.
Expenses Paid, Amount $ 4 [9],[10]
Expense Ratio, Percent 0.09% [10],[11]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $10,000 investment in the Premier Shares class of the Portfolio at inception on June 11, 2024 and compares the initial and subsequent account values at the end of the completed fiscal year since inception.
GROWTH OF $10,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns Since
Inception
TREASURY INSTRUMENTS PORTFOLIO (PREMIER SHARES/NPYXX) 2.37%
Performance Inception Date Jun. 11, 2024
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 2,131,704,000
Holdings Count | Holding 28
Advisory Fees Paid, Amount $ 65,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $2,131,704
Total number of portfolio holdings 28
Total net advisory fees paid (in thousands) $65
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
U.S. Government Obligations 100.3%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
C000193056 [Member]  
Shareholder Report [Line Items]  
Fund Name TREASURY INSTRUMENTS PORTFOLIO
Class Name SHARES
Trading Symbol NTYXX
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about the Treasury Instruments Portfolio (the “Portfolio”) for the period of October 7, 2024 (Commencement of Class Operations) to November 30, 2024.
Shareholder Report Annual or Semi-Annual annual shareholder report
Additional Information [Text Block] You can find additional information about the Portfolio at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature. You can also request this information by contacting us at 800-637-1380.
Additional Information Phone Number 800-637-1380
Additional Information Website ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#literature
Expenses [Text Block]
What were the Portfolio costs for the last year?
(Based on a hypothetical $10,000 investment)
Portfolio (Class) Cost of $10,000 Investment1 Costs paid as a percentage of a $10,000 investment1,2
TREASURY INSTRUMENTS PORTFOLIO
(SHARES/NTYXX)		 $1* 0.04%
​*
For the period from October 7, 2024 (Commencement of Class Operations) through November 30, 2024.
​1
Reflects applicable expense reimbursements and fee waivers.
​2
Expense ratio is expressed on an annualized basis.
Expenses Paid, Amount $ 1 [12],[13]
Expense Ratio, Percent 0.04% [13],[14]
Performance Past Does Not Indicate Future [Text] The Portfolio's past performance is not a good predictor of the Portfolio's future performance.
Line Graph [Table Text Block]
Portfolio Performance
The following graph assumes an initial $5,000,000 investment in the Shares class of the Portfolio at inception on October 7, 2024 and compares the initial and subsequent account values at the end of the completed fiscal year since inception.
GROWTH OF $5,000,000
Fund Performance - Growth of 10K
Average Annual Return [Table Text Block]
Average Annual Total Returns Since
Inception
TREASURY INSTRUMENTS PORTFOLIO (SHARES/NTYXX) 0.70%
Performance Inception Date Oct. 07, 2024
No Deduction of Taxes [Text Block] The graph and table above do not reflect the deduction of taxes that a shareholder would pay on Portfolio distributions or redemption of Portfolio shares.
Updated Performance Information Location [Text Block]
Performance data current to the most recent month-end is available at ntam.northerntrust.com/united-states/institutional/strategies/cash/northern-institutional-funds#performance.
Net Assets $ 2,131,704,000
Holdings Count | Holding 28
Advisory Fees Paid, Amount $ 65,000
Additional Fund Statistics [Text Block]
KEY PORTFOLIO STATISTICS
Portfolio net assets (in thousands) $2,131,704
Total number of portfolio holdings 28
Total net advisory fees paid (in thousands) $65
Holdings [Text Block]
TYPE OF SECURITY AS A % OF NET ASSETS
U.S. Government Obligations 100.3%
Figures in the above table may not sum to 100% due to the exclusions of other assets and liabilities.
[1] Reflects applicable expense reimbursements and fee waivers.
[2] Reflects applicable expense reimbursements and fee waivers.
[3] Reflects applicable expense reimbursements and fee waivers.
[4] Reflects applicable expense reimbursements and fee waivers.
[5] Reflects applicable expense reimbursements and fee waivers.
[6] Reflects applicable expense reimbursements and fee waivers.
[7] Reflects applicable expense reimbursements and fee waivers.
[8] Reflects applicable expense reimbursements and fee waivers.
[9] For the period from June 11, 2024 (Commencement of Class Operations) through November 30, 2024.
[10] Reflects applicable expense reimbursements and fee waivers.
[11] Expense ratio is expressed on an annualized basis.
[12] For the period from October 7, 2024 (Commencement of Class Operations) through November 30, 2024.
[13] Reflects applicable expense reimbursements and fee waivers.
[14] Expense ratio is expressed on an annualized basis.