Fair Value Measurements (Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Recurring Basis)) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
servicing asset	$ 1,141	$ 926
Fair value - Derivative Assets	1,177		$ 1,114
Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at fair value on a recurring basis	190	136
Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at fair value on a recurring basis	11	11
Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at fair value on a recurring basis	$ (143)	$ (165)
Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	0.00%	0.50%
OAS spread (bps)	4.47%	4.46%
Lower Limit | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	(13.40%)	(12.60%)
Credit risk factor	0.00%	0.00%
Lower Limit | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	7.30%	9.50%
Lower Limit | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Mar. 31, 2021	Feb. 28, 2021
Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	100.00%	98.10%
OAS spread (bps)	15.13%	15.15%
Upper Limit | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	19.40%	14.10%
Credit risk factor	39.90%	46.20%
Upper Limit | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	96.60%	102.70%
Upper Limit | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Nov. 30, 2023	Dec. 31, 2023
Weighted average | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	0.60%	1.30%
Credit risk factor	0.50%	1.50%
Weighted average | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	78.90%	76.60%
Weighted average | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Jan. 06, 2022	Sep. 08, 2021
Weighted average | Fixed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	11.20%	10.00%
OAS spread (bps)	5.38%	5.48%
Weighted average | Adjustable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	23.10%	24.60%
OAS spread (bps)	8.84%	7.97%