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, 2020	Mar. 31, 2019
Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at FV	$ 185	$ 190
Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Mortgage Servicing Rights	685	1,141
Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative assets	69	11
Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative Liability	$ (171)	$ (143)
Minimum | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	(2.10%)	(13.40%)
Credit risk factor	0.00%	0.00%
Minimum | Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	0.50%	0.00%
OAS (bps)	536	447
Minimum | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	7.30%	7.30%
Minimum | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Jun. 30, 2022	Mar. 31, 2021
Maximum | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	13.10%	19.40%
Credit risk factor	40.60%	39.90%
Maximum | Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	97.00%	100.00%
OAS (bps)	1,513	1,513
Maximum | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	97.20%	96.60%
Maximum | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Mar. 31, 2024	Dec. 31, 2023
Weighted-average | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	2.20%	0.60%
Credit risk factor	0.70%	0.50%
Weighted-average | Mortgage Servicing Rights | Fixed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	19.50%	11.20%
OAS (bps)	926	538
Weighted-average | Mortgage Servicing Rights | Adjustable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	23.80%	23.10%
OAS (bps)	932	884
Weighted-average | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	70.10%	78.90%
Weighted-average | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Dec. 31, 2022	Mar. 31, 2022