Fair Value Measurements - Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative assets	$ 2,777		$ 2,677
Derivative liabilities	(3,223)		(2,999)
Servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Servicing rights	$ 1,756	$ 1,725
Servicing rights | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	0.00%	0.00%
OAS (bps)	0.0448	0.0477
Servicing rights | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	100.00%	100.00%
OAS (bps)	0.1833	0.1447
Servicing rights | Fixed | Weighted-Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	5.80%	5.60%
OAS (bps)	0.0460	0.0629
Servicing rights | Adjustable | Weighted-Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	22.90%	20.30%
OAS (bps)	0.0702	0.1204
IRLCs, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative assets	$ 5	$ 7
IRLCs, net | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	20.00%	22.30%
IRLCs, net | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	96.00%	97.50%
IRLCs, net | Weighted-Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	79.40%	82.50%
Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative liabilities	$ (162)	$ (192)
Swap | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the Covered Litigation	Jun. 30, 2026	Mar. 31, 2024
Swap | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the Covered Litigation	Mar. 31, 2028	Mar. 31, 2027
Swap | Weighted-Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the Covered Litigation	Dec. 31, 2026	Jun. 30, 2025
Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at FV	$ 113	$ 128	$ 116
Residential Mortgage | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	(25.20%)	(22.20%)
Credit risk factor	0.00%	0.00%
Residential Mortgage | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	3.70%	5.70%
Credit risk factor	0.60%	23.20%
Residential Mortgage | Weighted-Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	(13.40%)	(10.30%)
Credit risk factor	0.10%	0.50%