Total Equity and Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Net Unrealized Gains Losses on Non Otti Securities [Abstract]
Net unrealized gains (losses) on non-OTTI securities, after-tax, Beginning Balance	$ 743	$ (494)	$ (284)
Other comprehensive income (loss), non otti securities adjustment, after tax	151	(251)	1,178	$ (866)
Net unrealized gains (losses) on non-OTTI securities, after-tax, Ending Balance	894	(745)	894	(745)
Net Unrealized Gains Losses On Otti Securities [Abstract]
Net unrealized gains (losses) on OTTI securities, after tax, Beginning Balance	211	227	204
Other comprehensive income loss otti securities adjustment after tax	14	0	21	12
Net unrealized gains (losses) on OTTI securities, after tax, Ending Balance	225	227	225	227
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	320	(52)	47
Other comprehensive income (loss), derivatives qualifying as hedges, net of tax	61	(54)		(290)
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification and tax	61	(54)	334	(290)
Net unrealized gains (losses) on cash flow hedge derivatives, after-tax, Ending balance	381	(106)	381	(106)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract]
Pension and other postretirement benefit plan adjustments, after tax, Beginning Balance	(483)	(489)	(530)
Pension and other postretirement benefit plan adjustments, net activity, After Tax	2	1	49	54
Pension and other postretirement benefit plan adjustments, after tax, Ending Balance	(481)	(488)	(481)	(488)
Other Comprehensive Income Other Adjustments [Abstract]
Other, after tax, Beginning balance	(160)	(132)	(162)
Total other, net activity, after tax	(22)	(16)	(20)	(28)
Other, after tax, Ending balance	(182)	(148)	(182)	(148)
Other Comprehensive Income (Loss) Total [Abstract]
Accumulated other comprehensive income (loss), net of tax, beginning balance	631	(940)	(725)
Cumulative effect of ASU adoptions						$ 16
Other comprehensive income (loss), after tax and net of reclassifications into Net income	206	(320)	1,562	(1,118)
Accumulated other comprehensive income (loss), net of tax, ending balance	837	(1,260)	837	(1,260)
Accumulated other comprehensive income (loss), net of tax, adjusted balance					$ (142)
Previously Reported [Member]
Net Unrealized Gains Losses on Non Otti Securities [Abstract]
Net unrealized gains (losses) on non-OTTI securities, after-tax, Beginning Balance				62
Net Unrealized Gains Losses On Otti Securities [Abstract]
Net unrealized gains (losses) on OTTI securities, after tax, Beginning Balance				215
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				151
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract]
Pension and other postretirement benefit plan adjustments, after tax, Beginning Balance				(446)
Other Comprehensive Income Other Adjustments [Abstract]
Other, after tax, Beginning balance				(130)
Other Comprehensive Income (Loss) Total [Abstract]
Accumulated other comprehensive income (loss), net of tax, beginning balance				(148)
Net unrealized gains (losses) on non-OTTI securities [Member] | Accounting Standards Update 2018-02 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of ASU adoptions					59
Net unrealized gains (losses) on cash flow hedge derivatives [Member] | Accounting Standards Update 2018-02 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of ASU adoptions					33
Pension and other postretirement benefit plan adjustments [Member] | Accounting Standards Update 2018-02 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of ASU adoptions					(96)
Other [Member] | Accounting Standards Update 2018-02 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of ASU adoptions					10
Total [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of ASU adoptions						$ (6)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	$ 206	$ (320)	$ 1,562	$ (1,118)
Total [Member] | Accounting Standards Update 2018-02 [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Cumulative effect of ASU adoptions					$ 6