Leases - Schedule of Operating Leases Included on Consolidated Statement of Financial Condition (Detail) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Leases [Abstract] | ||
| Operating lease ROU assets | $ 649 | $ 669 |
| Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List] | us-gaap:OtherAssets | us-gaap:OtherAssets |
| Operating lease liabilities | $ 755 | $ 776 |
| Operating Lease, Liability, Statement of Financial Position [Extensible List] | us-gaap:OtherLiabilities | us-gaap:OtherLiabilities |