Total Equity and Other Comprehensive Income (Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Tax [Abstract]
Net unrealized gains (losses) on securities, pre-tax	$ 55	$ 579	$ (1,126)	$ 2,241
Less: Net realized gains (losses) reclassified to earnings	9	41	22	223
Net increase (decrease), pre-tax	46	538	(1,148)	2,018
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax [Abstract]
Net unrealized gains (losses) on securities, tax effect	(13)	(134)	265	(515)
Less: Net realized gains (losses) reclassified to earnings, tax effect	(2)	(9)	(5)	(51)
Effect of income taxes	(11)	(125)	270	(464)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, After Reclassification Adjustments, after Tax [Abstract]
Net unrealized gains (losses) on securities, after tax	42	445	(861)	1,726
Less: Net realized gains (losses) reclassified to earnings, after tax	7	32	17	172
Net increase (decrease), after-tax	35	413	(878)	1,554
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, pre-tax	330	115	(310)	945
Less: Net realized gains (losses) reclassified to earnings, pre-tax	108	103	243	148
Net increase (decrease), pre-tax	222	12	(553)	797
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, tax effect	(78)	(27)	73	(217)
Less: Net realized gains (losses) reclassified to earnings, tax effect	(25)	(24)	(57)	(34)
Effect of income taxes	(53)	(3)	130	(183)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract]
Net unrealized gains (losses) on cash flow hedges, after tax	252	88	(237)	728
Less: Net realized gains (losses) reclassified to earnings, after tax	83	79	186	114
Net increase (decrease), after-tax	169	9	(423)	614
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	(43)	(17)	(13)	(5)
Net increase (decrease), pre-tax	(43)	(17)	(13)	(5)
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	10	4	3	1
Effect of income taxes	10	4	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	(33)	(13)	(10)	(4)
Net increase (decrease), after-tax	(33)	(13)	(10)	(4)
Other Comprehensive Income Other Adjustments [Abstract]
Net unrealized gains (losses) on other transactions, pre-tax		2	1	10
Net increase (decrease), pre-tax		2	1	10
Net unrealized gains (losses) on other transactions, tax effect	2	(1)	3	(19)
Effect of income taxes	2	(1)	3	(19)
Net unrealized gains (losses) on other transactions, after tax	2	1	4	(9)
Net increase (decrease), after-tax	2	1	4	(9)
Other comprehensive income (loss), before tax and net of reclassifications into Net income	225	717	(1,713)	2,968
Total other comprehensive income (loss), tax effect	(52)	(166)	406	(698)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	173	551	(1,307)	2,270
Continuing Operations
Other Comprehensive Income Other Adjustments [Abstract]
Net unrealized gains (losses) on other transactions, pre-tax		2	1	10
Other comprehensive income (loss), before tax and net of reclassifications into Net income	225	535	(1,713)	2,820
Total other comprehensive income (loss), tax effect	(52)	(125)	406	(665)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	$ 173	410	(1,307)	2,155
Discontinued Operations
Other Comprehensive Income Other Adjustments [Abstract]
Other comprehensive income (loss), before tax and net of reclassifications into Net income		182		148
Total other comprehensive income (loss), tax effect		(41)		(33)
Other comprehensive income (loss), after tax and net of reclassifications into Net income		$ 141		$ 115