Other Comprehensive Income (Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Other comprehensive income (loss), before tax and net of reclassifications into Net income	$ 1,514	$ 3,227	$ (13,787)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax [Abstract]
Income tax benefit (expense) related to items of other comprehensive income	(367)	(767)	3,206
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, After Reclassification Adjustments, after Tax [Abstract]
Other comprehensive income (loss), after tax and net of reclassifications into Net income	1,147	2,460	(10,581)
Debt securities
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Net unrealized gains (losses)	(363)	840	(10,866)
Less: Net realized gains (losses) reclassified to earnings	(1,328)	(913)	(723)
Other comprehensive income (loss), before tax and net of reclassifications into Net income	965	1,753	(10,143)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax [Abstract]
Net unrealized gains (losses)	89	(202)	2,561
Less: Net realized gains (losses) reclassified to earnings	323	217	171
Income tax benefit (expense) related to items of other comprehensive income	(234)	(419)	2,390
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, After Reclassification Adjustments, after Tax [Abstract]
Net unrealized gains (losses)	(274)	638	(8,305)
Less: Net realized gains (losses) reclassified to earnings	(1,005)	(696)	(552)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	731	1,334	(7,753)
Cash flow hedge derivatives
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Net unrealized gains (losses)	(790)	(237)	(3,536)
Less: Net realized gains (losses) reclassified to earnings	(1,317)	(1,540)	(260)
Other comprehensive income (loss), before tax and net of reclassifications into Net income	527	1,303	(3,276)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax [Abstract]
Net unrealized gains (losses)	192	65	833
Less: Net realized gains (losses) reclassified to earnings	320	376	61
Income tax benefit (expense) related to items of other comprehensive income	(128)	(311)	772
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, After Reclassification Adjustments, after Tax [Abstract]
Net unrealized gains (losses)	(598)	(172)	(2,703)
Less: Net realized gains (losses) reclassified to earnings	(997)	(1,164)	(199)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	399	992	(2,504)
Pension and other postretirement benefit plan adjustments
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Less: Net realized gains (losses) reclassified to earnings	21	166	(363)
Other comprehensive income (loss), before tax and net of reclassifications into Net income	21	166	(363)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax [Abstract]
Less: Net realized gains (losses) reclassified to earnings	(5)	(40)	85
Income tax benefit (expense) related to items of other comprehensive income	(5)	(40)	85
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, After Reclassification Adjustments, after Tax [Abstract]
Less: Net realized gains (losses) reclassified to earnings	16	126	(278)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	16	126	(278)
Other
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Less: Net realized gains (losses) reclassified to earnings	1	5	(5)
Other comprehensive income (loss), before tax and net of reclassifications into Net income	1	5	(5)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax [Abstract]
Less: Net realized gains (losses) reclassified to earnings		3	(41)
Income tax benefit (expense) related to items of other comprehensive income		3	(41)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, After Reclassification Adjustments, after Tax [Abstract]
Less: Net realized gains (losses) reclassified to earnings	1	8	(46)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	$ 1	$ 8	$ (46)