Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Commitments to Extend Credit (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Total unfunded credit commitments	$ 44,685	$ 44,016
Allowance for credit losses: loans	421	422	$ 392	$ 448
Loan commitments
Financing Receivable, Allowance for Credit Loss [Line Items]
Total unfunded credit commitments	40,737	40,327
Standby letters of credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Total unfunded credit commitments	3,843	3,612
Commercial letters of credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Total unfunded credit commitments	105	77
Unfunded Credit Commitments
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses: loans	$ 175	$ 171	$ 105	$ 121