Comprehensive Income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	$ (616)	$ (1,066)
Unrealized holding gains (losses), net, before tax	(13)	89
Foreign currency translation adjustment, before tax	(2)	2
Unrealized losses on cash flow hedges	(243)	51
Total other comprehensive income (loss) before reclassifications, before tax	(258)	142
Losses realized in net income	1
Net yield adjustment from cash flow hedges currently in effect, before tax	87	59
Amortization of actuarial losses, before tax	(1)	(2)
Total other comprehensive income (loss), before tax	(171)	199
Ending balance, before tax	(787)	(867)
Beginning balance, tax	157	276
Unrealized holding gains (losses), net, tax	2	(24)
Foreign currency translation adjustment, tax		(1)
Unrealized losses on cash flow hedges, tax	60	(13)
Total other comprehensive income (loss) before reclassifications, tax	62	(38)
Net yield adjustment from cash flow hedges currently in effect, tax	(21)	(16)
Total other comprehensive income (loss), tax	41	(54)
Ending balance, tax	198	222
Beginning balance, net of tax	(459)	(790)
Unrealized holding gains (losses), net of tax	(11)	65
Foreign currency translation adjustments, net of tax	(2)	1
Unrealized losses on cash flow hedges, net of tax	(183)	38
Total other comprehensive income (loss) before reclassifications, net of tax	(196)	104
Losses realized in net income, net of tax	1
Net yield adjustment from cash flow hedges currently in effect, net of tax	66	43
Amortization of actuarial losses, net of tax	(1)	(2)
Total other comprehensive income (loss)	(130)	145
Ending balance, net of tax	(589)	(645)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(203)	(336)
Unrealized losses on cash flow hedges	(243)	51
Total other comprehensive income (loss) before reclassifications, before tax	(243)	51
Net yield adjustment from cash flow hedges currently in effect, before tax	87	59
Total other comprehensive income (loss), before tax	(156)	110
Ending balance, before tax	(359)	(226)
Total other comprehensive income (loss)	(117)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(155)	(273)
Amortization of actuarial losses, before tax	(1)	(2)
Total other comprehensive income (loss), before tax	(1)	(2)
Ending balance, before tax	(156)	(275)
Total other comprehensive income (loss)	(1)
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(7)	(13)
Foreign currency translation adjustment, before tax	(2)	2
Total other comprehensive income (loss) before reclassifications, before tax	(2)	2
Total other comprehensive income (loss), before tax	(2)	2
Ending balance, before tax	(9)	(11)
Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(251)	(444)
Unrealized holding gains (losses), net, before tax	(13)	89
Total other comprehensive income (loss) before reclassifications, before tax	(13)	89
Losses realized in net income	1
Total other comprehensive income (loss), before tax	(12)	89
Ending balance, before tax	(263)	$ (355)
Total other comprehensive income (loss)	$ (10)