Comprehensive Income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	$ (1,066)	$ (171)	$ (84)
Unrealized holding gains (losses), net, before tax	193	(551)	(95)
Foreign currency translation adjustment, before tax	5	(8)	(1)
Unrealized losses on cash flow hedges	(116)	(461)	(32)
Current year benefit plans gains, before tax	125	71	206
Total other comprehensive income (loss) before reclassifications, before tax	207	(949)	78
Amortization of unrealized holding losses on held-to-maturity securities		2	4
Net yield adjustment from cash flow hedges currently in effect, before tax	250	36	(253)
Amortization of prior service credit, before tax	(2)	(2)	(4)
Amortization of actuarial gains (losses), before tax	(5)	18	88
Total other comprehensive income (loss), before tax	450	(895)	(87)
Ending balance, before tax	(616)	(1,066)	(171)
Beginning balance, tax	276	44	22
Unrealized holding gains (losses), net, tax	(51)	143	25
Foreign currency translation adjustment, tax	(1)	2
Unrealized losses on cash flow hedges, tax	30	119	8
Current year benefit plans gains, tax	(33)	(18)	(54)
Total other comprehensive income (loss) before reclassifications, tax	(55)	246	(21)
Amortization of unrealized holding losses on held-to-maturity securities, tax		(1)	(1)
Net yield adjustment from cash flow hedges currently in effect, tax	(66)	(9)	66
Amortization of prior service credit, tax	1		1
Amortization of actuarial gains (losses), tax	1	(4)	(23)
Total other comprehensive income (loss), tax	(119)	232	22
Ending balance, tax	157	276	44
Beginning balance, net of tax	(790)	(127)	(62)
Unrealized holding gains (losses), net of tax	142	(408)	(70)
Foreign currency translation adjustments, net of tax	4	(6)	(1)
Unrealized losses on cash flow hedges, net of tax	(86)	(342)	(24)
Current year benefit plans gains, net of tax	92	53	152
Total other comprehensive income (loss) before reclassifications, net of tax	152	(703)	57
Amortization of unrealized holding losses on held-to-maturity securities		1	3
Net yield adjustment from cash flow hedges currently in effect, net of tax	184	27	(187)
Amortization of prior service credit, net of tax	(1)	(2)	(3)
Amortization of actuarial gains (losses), net of tax	(4)	14	65
Total other comprehensive income (loss)	331	(663)	(65)
Ending balance, net of tax	(459)	(790)	(127)
Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(444)	105	196
Unrealized holding gains (losses), net, before tax	193	(551)	(95)
Total other comprehensive income (loss) before reclassifications, before tax	193	(551)	(95)
Amortization of unrealized holding losses on held-to-maturity securities		2	4
Total other comprehensive income (loss), before tax	193	(549)	(91)
Ending balance, before tax	(251)	(444)	105
Total other comprehensive income (loss)	142	(407)	(67)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(273)	(360)	(650)
Current year benefit plans gains, before tax	125	71	206
Total other comprehensive income (loss) before reclassifications, before tax	125	71	206
Amortization of prior service credit, before tax	(2)	(2)	(4)
Amortization of actuarial gains (losses), before tax	(5)	18	88
Total other comprehensive income (loss), before tax	118	87	290
Ending balance, before tax	(155)	(273)	(360)
Total other comprehensive income (loss)	87	65	214
Cash Flow Hedges and Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(349)	84	370
Foreign currency translation adjustment, before tax	5	(8)	(1)
Unrealized losses on cash flow hedges	(116)	(461)	(32)
Total other comprehensive income (loss) before reclassifications, before tax	(111)	(469)	(33)
Net yield adjustment from cash flow hedges currently in effect, before tax	250	36	(253)
Total other comprehensive income (loss), before tax	139	(433)	(286)
Ending balance, before tax	$ (210)	$ (349)	$ 84