Fair Value Measurements - Quantitative Information about Nonrecurring Fair Value Measurement of Assets and Liabilities Classified as Level 3 (Detail) - Fair Value, Nonrecurring $ in Millions	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	$ 395	$ 2,202
Consumer loans held for sale
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	14	1,766
Commercial loans held for sale
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	132	143
Commercial Loans
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	134	186
Level 3
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	143	2,001
Level 3 | Consumer loans held for sale
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	9	1,742
Level 3 | Commercial loans held for sale
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	0	68
Level 3 | Commercial Loans
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	$ 134	$ 186
Adjusted market price | Level 3 | Consumer loans held for sale | Minimum | Market comparables and internal assumptions
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	0.08	0.10
Adjusted market price | Level 3 | Consumer loans held for sale | Maximum | Market comparables and internal assumptions
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	0.66	1
Adjusted market price | Level 3 | Consumer loans held for sale | Weighted Average | Market comparables and internal assumptions
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	0.38	0.98
Adjusted market price | Level 3 | Commercial loans held for sale | Market comparables and internal assumptions
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs		0.94
Loss severity rates | Level 3 | Commercial Loans | Minimum | Valuation of third party appraisal on underlying collateral
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	0.07	0.02
Loss severity rates | Level 3 | Commercial Loans | Maximum | Valuation of third party appraisal on underlying collateral
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	0.60	0.76
Loss severity rates | Level 3 | Commercial Loans | Weighted Average | Valuation of third party appraisal on underlying collateral
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	0.21	0.23