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Net Capital Requirements - Additional Information (Detail) - USD ($) $ in Billions	Dec. 31, 2025	Dec. 31, 2024
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Net capital requirement in certain regulated subsidiaries	$ 2.2	$ 1.8

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- Definition

Net capital requirements.

+ References

No definition available.

+ Details

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Namespace Prefix:	blk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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- References

No definition available.

+ Details

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Namespace Prefix:	srt_
Data Type:	xbrli:stringItemType
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Period Type:	duration