Segment Information (Schedule Of Investment Advisory, Administration Fees, Securities Lending Revenue And Performance Fees, BlackRock Solutions And Advisory Revenue, Distribution Fees And Other Revenue) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
BlackRock Solutions and advisory	$ 128	$ 117	$ 382	$ 361
Distribution fees	19	23	58	78
Other revenue	46	45	143	158
Total revenue	2,320	2,225	6,798	6,854
Equity [Member]
Segment Reporting Information [Line Items]
Total revenue	1,073	1,078	3,196	3,404
Fixed Income [Member]
Segment Reporting Information [Line Items]
Total revenue	491	419	1,386	1,227
Multi-Asset Class [Member]
Segment Reporting Information [Line Items]
Total revenue	241	232	724	676
Alternatives [Member]
Segment Reporting Information [Line Items]
Total revenue	232	225	642	652
Cash Management [Member]
Segment Reporting Information [Line Items]
Total revenue	90	86	267	298
Total Level 3 Investments [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 2,127	$ 2,040	$ 6,215	$ 6,257