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Goodwill - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Jul. 31, 2025	Jul. 31, 2024	Jul. 31, 2023	Dec. 31, 2025
Goodwill [Roll Forward]
Impairment of goodwill	$ 0	$ 0	$ 0
Closing market price of common stock				$ 1,070
Book value per share				$ 360

X

- Definition

Book value of common stock per share.

+ References

No definition available.

+ Details

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Namespace Prefix:	blk_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Common stock price per share, closing price of period

+ References

No definition available.

+ Details

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X

- Definition

Amount of impairment loss from asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

+ References

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+ Details

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X

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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