Fair Value Measurement - Nonrecurring Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans held for investment	$ 0	$ 0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans held for investment	254,878	244,701
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans held for investment	126	305
Other assets	175	175
Total assets	301	480
Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans held for investment	0	0
Other assets	0	0
Total assets	0	0
Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans held for investment	126	305
Other assets	175	175
Total assets	301	480
Equity investments subject to Impairment	53
Equity investments accounted for under measurement alternative	15	25
Foreclosed property and repossessed assets, fair value disclosure	39	42
Long lived assets held for sale	$ 68	$ 108