Fair Value Measurements - Fair Values of Recurring Assets and Liabilities With Significant Unobservable L3 Inputs (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
servicing asset	$ 1,039	$ 959
Fair value - Derivative Assets	1,700		$ 1,114
Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured at fair value on a recurring basis	192	162
Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured at fair value on a recurring basis	14	11
Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans measured at fair value on a recurring basis	$ (151)	$ (164)
Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment speed	1.00%	0.50%
OAS spread (bps)	44100.00%	46100.00%
Lower Limit | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate risk factor	(9.50%)	(13.30%)
Credit risk factor	0.00%	0.00%
Lower Limit | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan closing rates	6.60%	12.20%
Lower Limit | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Timing of the resolution of the covered litigation	Jun. 30, 2021	Jan. 31, 2021
Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment speed	97.00%	97.00%
OAS spread (bps)	151300.00%	151300.00%
Upper Limit | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate risk factor	0.053%	0.119%
Credit risk factor	34.50%	0.403%
Upper Limit | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan closing rates	96.60%	0.966%
Upper Limit | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Timing of the resolution of the covered litigation	Dec. 31, 2023	Nov. 30, 2023
Weighted average | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate risk factor	(0.002%)	(0.001%)
Credit risk factor	0.006%	0.007%
Weighted average | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan closing rates	0.784%	0.809%
Weighted average | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Timing of the resolution of the covered litigation	Feb. 07, 2022	Sep. 06, 2021
Weighted average | Fixed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment speed	0.132%	0.095%
OAS spread (bps)	56100.00%	54300.00%
Weighted average | Adjustable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment speed	0.235%	0.236%
OAS spread (bps)	90900.00%	81700.00%