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, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Mortgage Servicing Rights	$ 993	$ 938
Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at FV	183	179
Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at FV	18	7
Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans measured at FV	$ (163)	$ (125)
Minimum | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	(9.20%)	(13.20%)
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%	0.50%
OAS (bps)	5.07%	4.41%
Minimum | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	7.30%	9.50%
Minimum | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Mar. 31, 2022	Mar. 31, 2021
Maximum | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	9.80%	9.40%
Credit risk factor	26.50%	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)	15.13%	15.13%
Maximum | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	97.10%	96.70%
Maximum | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Dec. 31, 2023	Dec. 31, 2023
Weighted-average | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate risk factor	(0.20%)	0.50%
Credit risk factor	0.50%	0.70%
Weighted-average | Mortgage Servicing Rights | Fixed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	13.00%	10.20%
OAS (bps)	6.02%	5.34%
Weighted-average | Mortgage Servicing Rights | Adjustable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Prepayment speed	22.60%	23.00%
OAS (bps)	9.21%	8.63%
Weighted-average | Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loan closing rates	81.70%	86.00%
Weighted-average | Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Timing of the resolution of the covered litigation	Sep. 30, 2022	Dec. 31, 2021