Commitments, Contingent Liabilities and Guarantees - Summary of Significant Commitments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Commitments to extend credit
Long-term Purchase Commitment
Commitments	$ 74,499	$ 75,696
Forward contracts related to residential mortgage loans held for sale
Long-term Purchase Commitment
Commitments	2,903	2,901
Letters of credit
Long-term Purchase Commitment
Commitments	1,982	2,137
Purchase obligations
Long-term Purchase Commitment
Commitments	195	113
Capital commitments for private equity investments
Long-term Purchase Commitment
Commitments	83	75
Capital expenditures
Long-term Purchase Commitment
Commitments	$ 75	$ 84