Total Equity and Other Comprehensive Income (Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Net unrealized gains (losses) on securities, pre-tax	$ (320)	$ 42	$ (1,446)	$ 2,283
Less: Net realized gains (losses) reclassified to earnings	3	32	25	255
Net increase (decrease), pre-tax	(323)	10	(1,471)	2,028
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax [Abstract]
Net unrealized gains (losses) on securities, tax effect	76	(9)	341	(525)
Less: Net realized gains (losses) reclassified to earnings, tax effect	(1)	(7)	(6)	(59)
Effect of income taxes	77	(2)	347	(466)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, After Reclassification Adjustments, after Tax [Abstract]
Net unrealized gains (losses) on securities, after tax	(244)	33	(1,105)	1,758
Less: Net realized gains (losses) reclassified to earnings, after tax	2	25	19	196
Net increase (decrease), after-tax	(246)	8	(1,124)	1,562
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, pre-tax	(59)	15	(369)	960
Less: Net realized gains (losses) reclassified to earnings, pre-tax	115	134	358	282
Net increase (decrease), pre-tax	(174)	(119)	(727)	678
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, tax effect	14	(3)	87	(221)
Less: Net realized gains (losses) reclassified to earnings, tax effect	(27)	(30)	(84)	(65)
Effect of income taxes	41	27	171	(156)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, after tax	(45)	12	(282)	739
Less: Net realized gains (losses) reclassified to earnings, after tax	88	104	274	217
Net increase (decrease), after-tax	(133)	(92)	(556)	522
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax [Abstract]
Net pension and other postretirement benefit plan activity and other reclassified to earnings, pre-tax	2	2	(11)	(3)
Net increase (decrease), pre-tax	2	2	(11)	(3)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax [Abstract]
Net pension and other postretirement benefit plan activity and other reclassified to earnings, tax effect			3	1
Effect of income taxes			3	1
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]
Net pension and other postretirement benefit plan activity and other reclassified to earnings, after-tax	2	2	(8)	(2)
Net increase (decrease), after-tax	2	2	(8)	(2)
Other Comprehensive Income Other Adjustments [Abstract]
Net unrealized gains (losses) on other transactions, pre-tax	1		2	10
Net increase (decrease), pre-tax	1		2	10
Net unrealized gains (losses) on other transactions, tax effect	(8)	10	(5)	(9)
Effect of income taxes	(8)	10	(5)	(9)
Net unrealized gains (losses) on other transactions, after tax	(7)	10	(3)	1
Net increase (decrease), after-tax	(7)	10	(3)	1
Other comprehensive income (loss), before tax and net of reclassifications into Net income	(494)	(107)	(2,207)	2,861
Total other comprehensive income (loss), tax effect	110	35	516	(663)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	(384)	(72)	(1,691)	2,198
Continuing Operations
Other Comprehensive Income Other Adjustments [Abstract]
Net unrealized gains (losses) on other transactions, pre-tax	1		2	10
Other comprehensive income (loss), before tax and net of reclassifications into Net income	(494)	(107)	(2,207)	2,713
Total other comprehensive income (loss), tax effect	110	35	516	(630)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	(384)	(72)	(1,691)	2,083
Discontinued Operations
Other Comprehensive Income Other Adjustments [Abstract]
Other comprehensive income (loss), before tax and net of reclassifications into Net income				148
Total other comprehensive income (loss), tax effect				(33)
Other comprehensive income (loss), after tax and net of reclassifications into Net income				$ 115