Total Equity and Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2018
Net Unrealized Gains Losses on Non Otti Securities [Abstract]
Net unrealized gains (losses) on non-OTTI securities, after-tax, Beginning Balance	$ 208	$ (375)	$ (284)	$ 62
Other comprehensive income (loss), non otti securities adjustment, after tax	535	(119)	1,027	(615)
Net unrealized gains (losses) on non-OTTI securities, after-tax, Ending Balance	743	(494)	743	(494)
Net Unrealized Gains Losses On Otti Securities [Abstract]
Net unrealized gains (losses) on OTTI securities, after tax, Beginning Balance	(211)	(225)	(204)	(215)
Other comprehensive income loss otti securities adjustment after tax		2	7	12
Net unrealized gains (losses) on OTTI securities, after tax, Ending Balance	(211)	(227)	(211)	(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	124	35	47	151
Other comprehensive income (loss), derivatives qualifying as hedges, net of tax	196	(87)		(236)
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification and tax	196		273
Net unrealized gains (losses) on cash flow hedge derivatives, after-tax, Ending balance	320	(52)	320	(52)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract]
Pension and other postretirement benefit plan adjustments, after tax, Beginning Balance	418	494	530	446
Pension and other postretirement benefit plan adjustments, net activity, After Tax	(65)	5	47	53
Pension and other postretirement benefit plan adjustments, after tax, Ending Balance	483	489	483	489
Other Comprehensive Income Other Adjustments [Abstract]
Other, after tax, Beginning balance	(130)	(90)	(162)	(130)
Total other, net activity, after tax	(30)	(42)	2	(12)
Other, after tax, Ending balance	(160)	(132)	(160)	(132)
Other Comprehensive Income (Loss) Total [Abstract]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(5)	(699)	(725)	(148)
Other comprehensive income (loss), after tax and net of reclassifications into Net income	636	(241)	1,356	(798)
Accumulated other comprehensive income (loss), net of tax, ending balance	631	(940)	631	(940)
Accumulated other comprehensive income (loss), net of tax, adjusted balance					$ (142)
Net unrealized gains (losses) on non-OTTI securities [Member] | Accounting Standards Update 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of ASU adoptions					59
Net unrealized gains (losses) on cash flow hedge derivatives [Member] | Accounting Standards Update 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of ASU adoptions					33
Pension and other postretirement benefit plan adjustments [Member] | Accounting Standards Update 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of ASU adoptions					(96)
Other [Member] | Accounting Standards Update 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of ASU adoptions					10
Total [Member]
Other Comprehensive Income (Loss) Total [Abstract]
Other comprehensive income (loss), after tax and net of reclassifications into Net income	$ 636	$ (241)	$ 1,356	$ (798)
Total [Member] | Accounting Standards Update 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of ASU adoptions					$ 6