Accumulated Other Comprehensive Income - Activity in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax unrealized losses	$ (196)	$ 823	$ (8,284)
Other comprehensive income (loss), tax effect	47	(200)	1,967
Other comprehensive (loss) income, net of tax	(149)	623	(6,317)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	19,172	17,327	22,210
Other comprehensive (loss) income, net of tax	(149)	623	(6,317)
Ending Balance	19,645	19,172	17,327
AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive (loss) income, net of tax	(149)	623	(6,317)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(4,487)	(5,110)	1,207
Other comprehensive (loss) income, net of tax	(149)	623	(6,317)
Ending Balance	(4,636)	(4,487)	(5,110)
Net unrealized gains on available-for-sale debt securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Available-for-sale debt securities transferred to held-to-maturity securities	27	656	(7,194)
Other comprehensive income (loss), before reclassifications, tax effect	(12)	(162)	1,716
Other comprehensive income (loss), before reclassifications, net activity	15	494	(5,478)
Reclassification adjustment, pre-tax activity	18	1	(2)
Reclassification adjustment, tax effect	(4)	0	0
Reclassification adjustment, net activity	14	1	(2)
Pretax unrealized losses	1,039	657	(7,196)
Other comprehensive income (loss), tax effect	(225)	(162)	1,716
Other comprehensive (loss) income, net of tax	814	495	(5,480)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(4,094)	(4,589)	891
Other comprehensive (loss) income, net of tax	814	495	(5,480)
Ending Balance	(3,280)	(4,094)	(4,589)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale Transferred to Held-to-Maturity, Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Available-for-sale debt securities transferred to held-to-maturity securities	(994)
Other comprehensive income (loss), before reclassifications, tax effect	209
Other comprehensive income (loss), before reclassifications, net activity	(785)
Reclassification adjustment, pre-tax activity	129
Reclassification adjustment, tax effect	(28)
Reclassification adjustment, net activity	101
Pretax unrealized losses	(865)
Other comprehensive income (loss), tax effect	181
Other comprehensive (loss) income, net of tax	(684)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0
Other comprehensive (loss) income, net of tax	(684)
Ending Balance	(684)	0
Cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Available-for-sale debt securities transferred to held-to-maturity securities	(724)	(171)	(1,006)
Other comprehensive income (loss), before reclassifications, tax effect	172	40	232
Other comprehensive income (loss), before reclassifications, net activity	(552)	(131)	(774)
Reclassification adjustment, pre-tax activity	351	334	(99)
Reclassification adjustment, tax effect	(81)	(77)	22
Reclassification adjustment, net activity	270	257	(77)
Pretax unrealized losses	(373)	163	(1,105)
Other comprehensive income (loss), tax effect	91	(37)	254
Other comprehensive (loss) income, net of tax	(282)	126	(851)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(372)	(498)	353
Other comprehensive (loss) income, net of tax	(282)	126	(851)
Ending Balance		(372)	(498)
Defined benefit pension plants, net
Accumulated Other Comprehensive Income (Loss) [Line Items]
Available-for-sale debt securities transferred to held-to-maturity securities	(2)	(1)	11
Other comprehensive income (loss), before reclassifications, tax effect	0	0	(2)
Other comprehensive income (loss), before reclassifications, net activity	(2)	(1)	9
Reclassification adjustment, pre-tax activity	3	4	6
Reclassification adjustment, tax effect	0	(1)	(1)
Reclassification adjustment, net activity	3	3	5
Pretax unrealized losses	1	3	17
Other comprehensive income (loss), tax effect	0	(1)	(3)
Other comprehensive (loss) income, net of tax	1	2	14
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(17)	(19)	(33)
Other comprehensive (loss) income, net of tax	1	2	14
Ending Balance	(16)	(17)	(19)
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax unrealized losses	2	0	0
Other comprehensive income (loss), tax effect	0	0	0
Other comprehensive (loss) income, net of tax	2	0	0
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(4)	(4)	(4)
Other comprehensive (loss) income, net of tax	2	0	0
Ending Balance	$ (2)	$ (4)	$ (4)