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, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Total revenue	$ 16,205	$ 14,539	$ 14,198
Revenue by Client Type [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	12,639	11,777	11,553
Revenue by Client Type [Member] \| Retail [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	3,651	3,411	3,413
Revenue by Client Type [Member] \| Institutional Active [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	2,342	2,172	2,044
Revenue by Client Type [Member] \| iShares ETFs [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	4,788	4,564	4,468
Revenue by Client Type [Member] \| Institutional Index [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	1,068	1,012	1,021
Revenue by Client Type [Member] \| Institutional [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	3,410	3,184	3,065
Revenue by Client Type [Member] \| Cash Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	790	618	607
Revenue by Client Type [Member] \| Long-term [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	11,849	11,159	10,946
Revenue by Investment Style [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	12,639	11,777	11,553
Revenue by Investment Style [Member] \| Active [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	5,914	5,510	5,391
Revenue by Investment Style [Member] \| Index and iShares ETFs [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	5,935	5,649	5,555
Revenue by Investment Style [Member] \| Cash Management [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	790	618	607
Revenue by Investment Style [Member] \| Long-term [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 11,849	$ 11,159	$ 10,946