Total Equity and Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jan. 01, 2020
Net Unrealized Gains Losses on Non Otti Securities [Abstract]
Other comprehensive income (loss), non otti securities adjustment, after tax		$ 535		$ 1,027
Net Unrealized Gains Losses On Otti Securities [Abstract]
Other comprehensive income loss otti securities adjustment after tax		0		7
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax [Abstract]
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification and tax	9	196	$ 614	273
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract]
Pension and other postretirement benefit plan adjustments, net activity, After Tax	(13)	(65)	(4)	47
Other Comprehensive Income Other Adjustments [Abstract]
Total other, net activity, after tax	1	(2)	(9)	6
Net unrealized gains (losses) on securities without an allowance for credit losses
Net unrealized gains (losses) on securities without an Allowance, net activity, after tax	477		1,623
Other Comprehensive Income (Loss) Total [Abstract]
Accumulated other comprehensive income (loss), net of tax, beginning balance			799
Other comprehensive income (loss), after tax and net of reclassifications into Net income	551	636	2,270	1,356
Accumulated other comprehensive income (loss), net of tax, ending balance	3,069		3,069
Continuing Operations
Other Comprehensive Income (Loss) Total [Abstract]
Other comprehensive income (loss), after tax and net of reclassifications into Net income	410	664	2,155	1,360
Discontinued Operations [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Other comprehensive income (loss), after tax and net of reclassifications into Net income	141	(28)	115	(4)
Net unrealized gains (losses) on non-OTTI securities [Member]
Net Unrealized Gains Losses on Non Otti Securities [Abstract]
Net unrealized gains (losses) on non-OTTI securities, after-tax, Beginning Balance		208		(284)
Other comprehensive income (loss), non otti securities adjustment, after tax		535		1,027
Net unrealized gains (losses) on non-OTTI securities, after-tax, Ending Balance		743		743
Net unrealized gains (losses) on OTTI securities [Member]
Net Unrealized Gains Losses On Otti Securities [Abstract]
Net unrealized gains (losses) on OTTI securities, after tax, Beginning Balance		211		204
Other comprehensive income loss otti securities adjustment after tax				7
Net unrealized gains (losses) on OTTI securities, after tax, Ending Balance		211		211
Net unrealized gains (losses) on cash flow hedge derivatives [Member]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax [Abstract]
Net unrealized gains (losses) on cash flow hedge derivatives, after-tax, Beginning balance	881	124	276	47
Other comprehensive income (loss), derivatives qualifying as hedges, net of tax	9	196	614	273
Net unrealized gains (losses) on cash flow hedge derivatives, after-tax, Ending balance	890	320	890	320
Net unrealized gains (losses) on cash flow hedge derivatives [Member] | Accounting Standards Update 2016-03 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of new accounting principle in period of adoption
Pension and other postretirement benefit plan adjustments [Member]
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract]
Pension and other postretirement benefit plan adjustments, after tax, Beginning Balance	(399)	(418)	(408)	(530)
Pension and other postretirement benefit plan adjustments, net activity, After Tax	(13)	(65)	(4)	47
Pension and other postretirement benefit plan adjustments, after tax, Ending Balance	(412)	(483)	(412)	(483)
Pension and other postretirement benefit plan adjustments [Member] | Accounting Standards Update 2016-03 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of new accounting principle in period of adoption
Other [Member]
Other Comprehensive Income Other Adjustments [Abstract]
Other, after tax, Beginning balance	(31)	(35)	(21)	(43)
Total other, net activity, after tax	1	(2)	(9)	6
Other, after tax, Ending balance	(30)	(37)	(30)	(37)
Total [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Accumulated other comprehensive income (loss), net of tax, beginning balance	2,518	(5)	799	(725)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	551	636	2,270	1,356
Accumulated other comprehensive income (loss), net of tax, ending balance	3,069	631	3,069	631
Total [Member] | Accounting Standards Update 2016-03 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of new accounting principle in period of adoption
Total [Member] | Continuing Operations
Other Comprehensive Income (Loss) Total [Abstract]
Accumulated other comprehensive income (loss), net of tax, beginning balance	2,659	90	914	(606)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	410	664	2,155	1,360
Accumulated other comprehensive income (loss), net of tax, ending balance	3,069	754	3,069	754
Total [Member] | Continuing Operations | Accounting Standards Update 2016-03 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of new accounting principle in period of adoption
Total [Member] | Discontinued Operations [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(141)	(95)	(115)	(119)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	141	(28)	115	(4)
Accumulated other comprehensive income (loss), net of tax, ending balance		$ (123)		$ (123)
Net unrealized gains (losses) on securities without an Allowance [Member]
Net unrealized gains (losses) on securities without an allowance for credit losses
Net unrealized gains (losses) on securities without an Allowance, after Tax, beginning balance	2,213		844
Net unrealized gains (losses) on securities without an Allowance, net activity, after tax	477		1,623
Net unrealized gains (losses) on securities without an Allowance, after Tax, ending balance	2,690		2,690
Net unrealized gains (losses) on securities without an Allowance [Member] | Accounting Standards Update 2016-03 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of new accounting principle in period of adoption					223
Net unrealized gains (losses) on securities with an Allowance [Member]
Net unrealized gains (losses) on securities with an allowance for credit losses
Net unrealized gains (losses) on securities with an Allowance, after Tax, beginning balance	(5)		223
Net unrealized gains (losses) on securities with an Allowance, net activity, after tax	(64)		(69)
Net unrealized gains (losses) on securities with an Allowance, after Tax, ending balance	$ (69)		$ (69)
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of new accounting principle in period of adoption					$ (223)