Accumulated Other Comprehensive Income - Activity in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), pre-tax activity	$ (2,187)	$ (3,472)	$ (2,260)	$ (8,481)
Other comprehensive income (loss), tax effect	514	810	531	1,968
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			17,327
Other comprehensive loss, net of tax	(1,673)	(2,662)	(1,729)	(6,513)
Ending balance	16,544		16,544
AOCI
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(5,166)	(2,644)	(5,110)	1,207
Other comprehensive loss, net of tax	(1,673)	(2,662)	(1,729)	(6,513)
Ending balance	(6,839)	(5,306)	(6,839)	(5,306)
Available-for-sale debt securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, pre-tax activity	(1,594)	(2,780)	(1,638)	(7,249)
Other comprehensive income (loss), before reclassifications, tax effect	376	651	386	1,685
Other comprehensive income (loss), before reclassifications, net activity	(1,218)	(2,129)	(1,252)	(5,564)
Reclassification adjustment, pre-tax activity	0	0	1	(3)
Reclassification adjustment, tax effect	0	0	0	1
Reclassification adjustment, net activity	0	0	1	(2)
Other comprehensive income (loss), pre-tax activity	(1,594)	(2,780)	(1,637)	(7,252)
Other comprehensive income (loss), tax effect	376	651	386	1,686
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(4,622)	(2,546)	(4,589)	891
Other comprehensive loss, net of tax	(1,218)	(2,129)	(1,251)	(5,566)
Ending balance	(5,840)	(4,675)	(5,840)	(4,675)
Cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, pre-tax activity	(687)	(688)	(864)	(1,092)
Other comprehensive income (loss), before reclassifications, tax effect	160	158	200	252
Other comprehensive income (loss), before reclassifications, net activity	(527)	(530)	(664)	(840)
Reclassification adjustment, pre-tax activity	94	(4)	240	(140)
Reclassification adjustment, tax effect	(22)	1	(55)	31
Reclassification adjustment, net activity	72	(3)	185	(109)
Other comprehensive income (loss), pre-tax activity	(593)	(692)	(624)	(1,232)
Other comprehensive income (loss), tax effect	138	159	145	283
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(522)	(63)	(498)	353
Other comprehensive loss, net of tax	(455)	(533)	(479)	(949)
Ending balance	(977)	(596)	(977)	(596)
Defined benefit pension plants, net
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, pre-tax activity	0	(1)	0	(2)
Other comprehensive income (loss), before reclassifications, tax effect	0	0	0	0
Other comprehensive income (loss), before reclassifications, net activity	0	(1)	0	(2)
Reclassification adjustment, pre-tax activity	0	1	1	5
Reclassification adjustment, tax effect	0	0	0	(1)
Reclassification adjustment, net activity	0	1	1	4
Other comprehensive income (loss), pre-tax activity	0	0	1	3
Other comprehensive income (loss), tax effect	0	0	0	(1)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(18)	(31)	(19)	(33)
Other comprehensive loss, net of tax	0	0	1	2
Ending balance	(18)	(31)	(18)	(31)
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), pre-tax activity	0	0	0	0
Other comprehensive income (loss), tax effect	0	0	0	0
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(4)	(4)	(4)	(4)
Other comprehensive loss, net of tax	0	0	0	0
Ending balance	$ (4)	$ (4)	$ (4)	$ (4)