Total Equity and Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Unrealized Gains Losses on Non Otti Securities [Abstract]
Net unrealized gains (losses) on non-OTTI securities, after-tax, Beginning Balance	$ 189	$ 778	$ 52	$ 286
Other Comprehensive Income (Loss), Non Otti Securities Adjustment, After Tax	41	(15)	178	477
Net unrealized gains (losses) on non-OTTI securities, after-tax, Ending Balance	230	763	230	763
Net Unrealized Gains Losses On Otti Securities [Abstract]
Net unrealized gains (losses) on OTTI securities, after tax, Beginning Balance	166	53	106	66
Other Comprehensive Income Loss Otti Securities Adjustment After Tax	44	24	104	11
Net unrealized gains (losses) on OTTI securities, after tax, Ending Balance	210	77	210	77
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax [Abstract]
Net unrealized gains (losses) on cash flow hedge derivatives, after-tax, Beginning balance	278	597	333	430
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	(30)	(80)	(85)	87
Net unrealized gains (losses) on cash flow hedge derivatives, after-tax, Ending balance	248	517	248	517
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Tax, [Abstract]
Pension and other postretirement benefit plan adjustments, after tax, Beginning Balance	(564)	(544)	(553)	(554)
Pension and other postretirement benefit plan adjustments, net activity, After Tax	7	6	(4)	16
Pension and other postretirement benefit plan adjustments, after tax, Ending Balance	(557)	(538)	(557)	(538)
Other Comprehensive Income Other Adjustments [Abstract]
Other, after tax, Beginning balance	(167)	(148)	(203)	(98)
Total Other, net activity, After tax	14	(25)	50	(75)
Other, after tax, Ending balance	(153)	(173)	(153)	(173)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(98)	736	(265)	130
Other comprehensive income (loss), after tax and net of reclassifications into Net income	76	(90)	243	516
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (22)	$ 646	$ (22)	$ 646