Commitments, Contingent Liabilities and Guarantees - Summary of Significant Commitments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Commitments to extend credit
Long-term Purchase Commitment
Commitments	$ 73,903	$ 75,696
Forward contracts related to residential mortgage loans held for sale
Long-term Purchase Commitment
Commitments	3,087	2,901
Letters of credit
Long-term Purchase Commitment
Commitments	1,900	2,137
Purchase obligations
Long-term Purchase Commitment
Commitments	132	113
Capital commitments for private equity investments
Long-term Purchase Commitment
Commitments	86	75
Capital expenditures
Long-term Purchase Commitment
Commitments	$ 80	$ 84