Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary of Commercial and Standby Letters of Credit (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Guarantor Obligations [Line Items]
Expires in One Year or Less	$ 3,289
Expires After One Year	162
Total Amount Outstanding	3,451	$ 3,007
Maximum Amount of Future Payments	3,451
Financial standby letters of credit
Guarantor Obligations [Line Items]
Expires in One Year or Less	3,146
Expires After One Year	107
Total Amount Outstanding	3,253
Maximum Amount of Future Payments	3,253
Performance standby letters of credit
Guarantor Obligations [Line Items]
Expires in One Year or Less	116
Expires After One Year	21
Total Amount Outstanding	137
Maximum Amount of Future Payments	137
Commercial letters of credit
Guarantor Obligations [Line Items]
Expires in One Year or Less	27
Expires After One Year	34
Total Amount Outstanding	61
Maximum Amount of Future Payments	$ 61