Commitments, Contingent Liabilities and Guarantees - Summary of Significant Commitments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Commitments to extend credit
Long-term Purchase Commitment
Commitments	$ 76,820	$ 74,499
Forward contracts related to residential mortgage loans held for sale
Long-term Purchase Commitment
Commitments	6,872	2,903
Letters of credit
Long-term Purchase Commitment
Commitments	1,869	1,982
Purchase obligations
Long-term Purchase Commitment
Commitments	177	195
Capital commitments for private equity investments
Long-term Purchase Commitment
Commitments	94	83
Capital expenditures
Long-term Purchase Commitment
Commitments	$ 84	$ 75