Fair Value Measurements (Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Recurring Basis)) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at FV	$ 179	$ 137
Fair value - Derivative Assets	1,114	823
Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at FV	179	137
Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Mortgage Servicing Rights	938	858
IRLCs, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value - Derivative Assets	7	8
Swap associated with the sale of Visa, Inc. Class B shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value - Derivative Assets	$ (125)	$ (137)
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	0.50%	0.00%
OAS spread (bps)	4.41%	4.50%
Minimum | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	(13.20%)	(10.60%)
Credit risk factor	0.00%	0.00%
Minimum | IRLCs, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	9.50%	12.50%
Minimum | Swap associated with the sale of Visa, Inc. Class B shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Jan. 31, 2021	Dec. 31, 2020
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	100.00%	98.10%
OAS spread (bps)	15.13%	15.15%
Maximum | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	9.40%	14.50%
Credit risk factor	39.90%	52.10%
Maximum | IRLCs, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	96.70%	97.70%
Maximum | Swap associated with the sale of Visa, Inc. Class B shares
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 | Fixed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	10.20%	11.40%
OAS spread (bps)	5.43%	5.49%
Weighted-average | Adjustable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	23.00%	24.60%
OAS spread (bps)	8.63%	7.85%
Weighted-average | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	0.50%	3.10%
Credit risk factor	0.70%	1.40%
Weighted-average | IRLCs, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	86.00%	71.80%
Weighted-average | Swap associated with the sale of Visa, Inc. Class B shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Nov. 11, 2021	Aug. 15, 2021