Revenue - Summary of Investment Advisory, Administration Fees and Securities Lending Revenue by Client Type and Investment Style (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Total revenue	$ 14,539	$ 14,198	$ 13,600
Revenue by Client Type [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	11,777	11,553	10,868
Revenue by Client Type [Member] \| Retail [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	3,411	3,413	3,250
Revenue by Client Type [Member] \| Institutional Active [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	2,172	2,044	1,955
Revenue by Client Type [Member] \| iShares ETFs [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	4,564	4,468	4,113
Revenue by Client Type [Member] \| Institutional Index [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	1,012	1,021	992
Revenue by Client Type [Member] \| Institutional [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	3,184	3,065	2,947
Revenue by Client Type [Member] \| Cash Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	618	607	558
Revenue by Client Type [Member] \| Long-term [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	11,159	10,946	10,310
Revenue by Investment Style [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	11,777	11,553	10,868
Revenue by Investment Style [Member] \| Active [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	5,510	5,391	5,152
Revenue by Investment Style [Member] \| Index and iShares ETFs [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	5,649	5,555	5,158
Revenue by Investment Style [Member] \| Cash Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	618	607	558
Revenue by Investment Style [Member] \| Long-term [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 11,159	$ 10,946	$ 10,310