Commitments, Contingent Liabilities and Guarantees - Summary of Significant Commitments (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Commitments to extend credit
Long-term Purchase Commitment
Commitments	$ 80,316	$ 74,499
Forward contracts related to residential mortgage loans held for sale
Long-term Purchase Commitment
Commitments	4,102	2,903
Letters of credit
Long-term Purchase Commitment
Commitments	1,908	1,982
Purchase obligations
Long-term Purchase Commitment
Commitments	177	195
Capital commitments for private equity investments
Long-term Purchase Commitment
Commitments	108	83
Capital expenditures
Long-term Purchase Commitment
Commitments	$ 77	$ 75