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, 2024	Dec. 31, 2023	Dec. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 26,957	$ 25,318	$ 17,903
Other comprehensive income before reclassifications:		125
Other comprehensive income (loss) before reclassifications, tax		(33)
OCI, before reclassifications, net of tax, attributable to parent		92
Ending balance	29,027	26,957	25,318
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, attributable to parent, beginning balance	(616)	(1,066)	(171)
Beginning balance	157	276	44
Beginning balance	(459)	(790)	(127)
Other comprehensive income before reclassifications:	37	207	(949)
Other comprehensive income (loss) before reclassifications, tax	(8)	(55)	246
OCI, before reclassifications, net of tax, attributable to parent	29	152	(703)
Total other comprehensive income (loss)	397	450	(895)
Deferred income taxes and tax credits	(102)	(119)	232
Other comprehensive income (loss), net of tax, portion attributable to parent	295	331	(663)
Equity, attributable to parent, ending balance	(219)	(616)	(1,066)
Ending balance	55	157	276
Ending balance	(164)	(459)	(790)
Investment Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, attributable to parent, beginning balance	(251)	(444)	105
Beginning balance	(187)	(329)	78
Other comprehensive income before reclassifications:	31	193	(551)
Other comprehensive income (loss) before reclassifications, tax	(8)	(51)	143
OCI, before reclassifications, net of tax, attributable to parent	23	142	(408)
Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:	15		2
Amortization of prior service credit, tax	(4)		(1)
Reclassification from AOCI, current period, net of tax, attributable to parent	11		1
Total other comprehensive income (loss)	46	193	(549)
Equity, attributable to parent, ending balance	(205)	(251)	(444)
Ending balance	(153)	(187)	(329)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, attributable to parent, beginning balance	(203)	(337)	88
Beginning balance	(151)	(249)	66
Other comprehensive income before reclassifications:	(296)	(116)	(461)
Other comprehensive income (loss) before reclassifications, tax	77	30	119
OCI, before reclassifications, net of tax, attributable to parent	(219)	(86)	(342)
Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:	364	250	36
Amortization of prior service credit, tax	(95)	(66)	(9)
Reclassification from AOCI, current period, net of tax, attributable to parent	269	184	27
Total other comprehensive income (loss)	68	134	(425)
Equity, attributable to parent, ending balance	(135)	(203)	(337)
Ending balance	(101)	(151)	(249)
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, attributable to parent, beginning balance	(155)	(273)	(360)
Beginning balance	(115)	(202)	(267)
Other comprehensive income before reclassifications:	305	125	71
Other comprehensive income (loss) before reclassifications, tax	(78)		(18)
OCI, before reclassifications, net of tax, attributable to parent	227		53
Total other comprehensive income (loss)	286	118	87
Equity, attributable to parent, ending balance	131	(155)	(273)
Ending balance	98	(115)	(202)
Prior Service Credit
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:	(2)	(2)	(2)
Amortization of prior service credit, tax	1	1	0
Reclassification from AOCI, current period, net of tax, attributable to parent	(1)	(1)	(2)
Actuarial Gains
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:	(5)	(5)	18
Amortization of prior service credit, tax	1	1	(4)
Reclassification from AOCI, current period, net of tax, attributable to parent	(4)	(4)	14
Settlement gain
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:	12
Amortization of prior service credit, tax	3
Reclassification from AOCI, current period, net of tax, attributable to parent	9
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, attributable to parent, beginning balance	(7)	(12)	(4)
Beginning balance	(6)	(10)	(4)
Other comprehensive income before reclassifications:	(3)	5	(8)
Other comprehensive income (loss) before reclassifications, tax	1	(1)	2
OCI, before reclassifications, net of tax, attributable to parent	(2)	4	(6)
Total other comprehensive income (loss)	(3)	5	(8)
Equity, attributable to parent, ending balance	(10)	(7)	(12)
Ending balance	$ (8)	$ (6)	$ (10)