Fair Value Measurements - Additional Information (Detail)	3 Months Ended			9 Months Ended
	Sep. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Weighted-average discount rates for fair value estimations				37.00%
Historical recovery rate of collateral values of consumer installment loans				43.00%
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Discount rates for fair value estimations				10.00%
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Discount rates for fair value estimations				90.00%
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Change in fair value of nonrecurring fair value measured loans for charge-offs and impairment reserves	$ 81,000,000		$ 116,000,000	$ 204,000,000	$ 269,000,000
Level 3 | Measurement Input, Commitment Expiration
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held-for-sale measurement input (as a percent)	0.06			0.06		0.05
Level 3 | Residential Mortgage Loans
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Capitalized servicing rights, valuation allowance		$ 0		$ 0	0
Nonrecurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	$ 805,000,000		804,000,000	805,000,000	804,000,000	$ 923,000,000
Nonrecurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	159,000,000		316,000,000	159,000,000	316,000,000	234,000,000
Nonrecurring | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	$ 646,000,000		$ 488,000,000	$ 646,000,000	$ 488,000,000	$ 689,000,000