Comprehensive Income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 26,957	$ 25,318
Ending balance	28,424	25,801
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, attributable to parent, beginning balance	(616)	(1,066)
Beginning balance	157	276
Beginning balance	(459)	(790)
Other comprehensive income (loss) before reclassifications:	(316)	(201)
Other comprehensive income (loss) before reclassifications, tax	78	48
OCI, before reclassifications, net of tax, attributable to parent	(238)	(153)
Total other comprehensive income (loss)	(120)	(96)
Deferred income taxes and credits	28	21
Other comprehensive income (loss), net of Tax, Portion attributable to parent	(92)	(75)
Equity, attributable to parent, ending balance	(736)	(1,162)
Ending balance	185	297
Ending balance	(551)	(865)
Investment Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, attributable to parent, beginning balance	(251)	(444)
Beginning balance	(187)
Other comprehensive income (loss) before reclassifications:	(1)	3
Other comprehensive income (loss) before reclassifications, tax	0	(2)
OCI, before reclassifications, net of tax, attributable to parent	(1)	1
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income:	13
Reclassification from AOCI, current period, tax	(4)
Reclassification from AOCI, current period, net of tax, attributable to parent	9
Total other comprehensive income (loss)	12	3
Equity, attributable to parent, ending balance	(239)	(441)
Ending balance	(179)
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, attributable to parent, beginning balance	(203)	(336)
Beginning balance	(151)
Other comprehensive income (loss) before reclassifications:	(313)	(208)
Other comprehensive income (loss) before reclassifications, tax	78	51
OCI, before reclassifications, net of tax, attributable to parent	(235)	(157)
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income:	186	108
Reclassification from AOCI, current period, tax	(46)	(27)
Reclassification from AOCI, current period, net of tax, attributable to parent	140	81
Total other comprehensive income (loss)	(127)	(100)
Equity, attributable to parent, ending balance	(330)	(436)
Ending balance	(246)
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, attributable to parent, beginning balance	(155)	(273)
Beginning balance	(115)
Other comprehensive income (loss) before reclassifications:	0	0
Total other comprehensive income (loss)	(3)	(3)
Equity, attributable to parent, ending balance	(158)	(276)
Ending balance	(118)
Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income:	(1)	(1)
Reclassification from AOCI, current period, tax	0	0
Reclassification from AOCI, current period, net of tax, attributable to parent	(1)	(1)
Actuarial Gains
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income:	(2)	(2)
Reclassification from AOCI, current period, tax	0	0
Reclassification from AOCI, current period, net of tax, attributable to parent	(2)	(2)
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Equity, attributable to parent, beginning balance	(7)	(13)
Beginning balance	(6)
Other comprehensive income (loss) before reclassifications:	(2)	4
Other comprehensive income (loss) before reclassifications, tax	0	(1)
OCI, before reclassifications, net of tax, attributable to parent	(2)	3
Total other comprehensive income (loss)	(2)	4
Equity, attributable to parent, ending balance	(9)	$ (9)
Ending balance	$ (8)