Segment Reporting - Segment Results and Reconciliations to GAAP - Core Earnings Adjustments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (loss) after provisions for loan losses	$ 116	$ 167	$ 256	$ 416
Goodwill and acquired intangible asset impairment and amortization	3	3	5	5
Income tax expense (benefit)	12	30	27	63
Net income	36	66	109	177
Total Adjustments [Member] | Adjustments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (loss) after provisions for loan losses	6	43	17	61
Total other income (loss)	(14)	(26)	(46)	(17)
Goodwill and acquired intangible asset impairment and amortization	(3)	(3)	(5)	(5)
Total Core Earnings adjustments to GAAP	(5)	20	(24)	49
Income tax expense (benefit)	(2)	(2)	(1)	5
Net income	(3)	22	(23)	44
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)	(3)	(5)	(5)
Total Core Earnings adjustments to GAAP	3	3	5	5
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	6	43	17	61
Total other income (loss)	(14)	(26)	(46)	(17)
Goodwill and acquired intangible asset impairment and amortization	0	0	0	0
Total Core Earnings adjustments to GAAP	$ (8)	$ 17	$ (29)	$ 44