Select [Member] Performance Management - Select		12 Months Ended
Oct. 31, 2025	Dec. 31, 2025
SELECT
Prospectus [Line Items]
Money Market Seven Day Yield		2.82%
FEDFUND
Prospectus [Line Items]
Bar Chart and Performance Table [Heading]	Performance Information
Performance Narrative [Text Block]	The information shows you how FedFund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. As with all such investments, past performance is not an indication of future results. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. The table includes all applicable fees. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. The Fund is a money market fund managed pursuant to the requirements of Rule 2a-7 under the 1940 Act. Updated information on the Fund’s performance can be obtained by visiting www.blackrock.com/cash or can be obtained by phone at (800) 441‑7450.
Performance Past Does Not Indicate Future [Text]	As with all such investments, past performance is not an indication of future results.
Performance Information Illustrates Variability of Returns [Text]	The information shows you how FedFund’s performance has varied year by year and provides some indication of the risks of investing in the Fund.
Bar Chart [Heading]	Select Shares ANNUAL TOTAL RETURNS FedFund As of 12/31
Bar Chart Closing [Text Block]	During the ten-year period shown in the bar chart, the highest return for a quarter was 1.12% (quarter ended December 31, 2023) and the lowest return for a quarter was 0.00% (quarter ended June 30, 2020).
Performance Table Heading	For the periods ended 12/31/25 Average Annual Total Returns
Performance Table Narrative	Current Yield: You may obtain the Fund’s current 7‑day yield by calling (800) 441‑7450 or by visiting the Fund’s website at www.blackrock.com/cash.
Money Market Seven Day Yield Phone	(800) 441‑7450
Performance Availability Website Address [Text]	www.blackrock.com/cash
Performance Availability Phone [Text]	(800) 441‑7450
FEDFUND \| SELECT
Prospectus [Line Items]
Highest Quarterly Return, Label [Optional Text]	highest return
Highest Quarterly Return	1.12%
Highest Quarterly Return, Date	Dec. 31, 2023
Lowest Quarterly Return, Label [Optional Text]	lowest return
Lowest Quarterly Return	none
Lowest Quarterly Return, Date	Jun. 30, 2020

Select [Member] Performance Management - Select

12 Months Ended

Oct. 31, 2025

Dec. 31, 2025

SELECT

Prospectus [Line Items]

Money Market Seven Day Yield

2.82%

FEDFUND

Prospectus [Line Items]

Bar Chart and Performance Table [Heading]

Performance Information

Performance Narrative [Text Block]

The information shows you how FedFund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. As with all such investments, past performance is not an indication of future results. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. The table includes all applicable fees. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. The Fund is a money market fund managed pursuant to the requirements of Rule 2a-7 under the 1940 Act. Updated information on the Fund’s performance can be obtained by visiting www.blackrock.com/cash or can be obtained by phone at (800) 441‑7450.

Performance Past Does Not Indicate Future [Text]

As with all such investments, past performance is not an indication of future results.

Performance Information Illustrates Variability of Returns [Text]

The information shows you how FedFund’s performance has varied year by year and provides some indication of the risks of investing in the Fund.

Bar Chart [Heading]

Select Shares ANNUAL TOTAL RETURNS FedFund As of 12/31

Bar Chart Closing [Text Block]

During the ten-year period shown in the bar chart, the highest return for a quarter was 1.12% (quarter ended December 31, 2023) and the lowest return for a quarter was 0.00% (quarter ended June 30, 2020).

Performance Table Heading

For the periods ended 12/31/25 Average Annual Total Returns

Performance Table Narrative

Current Yield: You may obtain the Fund’s current 7‑day yield by calling (800) 441‑7450 or by visiting the Fund’s website at www.blackrock.com/cash.

Money Market Seven Day Yield Phone

(800) 441‑7450

Performance Availability Website Address [Text]

www.blackrock.com/cash

Performance Availability Phone [Text]

(800) 441‑7450

FEDFUND | SELECT

Prospectus [Line Items]