Segment Reporting - Segment Results and Reconciliations to GAAP - Core Earnings Adjustments (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (loss) after provisions for loan losses	$ 219	$ 212	$ 634	$ 836
Goodwill and acquired intangible asset impairment and amortization	3	10	8	17
Income tax expense (benefit)	31	32	93	173
Net income	79	105	256	540
Total Adjustments [Member] | Adjustments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (loss) after provisions for loan losses	(11)	7	51	(104)
Total other income (loss)	(26)	(40)	(44)	(161)
Goodwill and acquired intangible asset impairment and amortization	(3)	(10)	(8)	(17)
Total Core Earnings adjustments to GAAP	(34)	(23)	15	(248)
Income tax expense (benefit)	(12)	(5)	(7)	(64)
Net income	(22)	(18)	22	(184)
Net Impact of Goodwill and Acquired Intangible Assets [Member] | Total Adjustments [Member] | Adjustments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (loss) after provisions for loan losses	0	0	0	0
Total other income (loss)	0	0	0	0
Goodwill and acquired intangible asset impairment and amortization	(3)	(10)	(8)	(17)
Total Core Earnings adjustments to GAAP	3	10	8	17
Net Impact of Derivative Accounting [Member] | Total Adjustments [Member] | Adjustments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (loss) after provisions for loan losses	(11)	7	51	(104)
Total other income (loss)	(26)	(40)	(44)	(161)
Goodwill and acquired intangible asset impairment and amortization	0	0	0	0
Total Core Earnings adjustments to GAAP	$ (37)	$ (33)	$ 7	$ (265)