Other Comprehensive Income (Accumulated Other Comprehensive Income (Loss) Components) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Unrealized Gains Losses on Non Otti Securities [Abstract]
Net unrealized gains (losses) on non-OTTI securities, after-tax, Beginning Balance	$ 647,000,000	$ 409,000,000	$ 1,177,000,000
Other Comprehensive Income (Loss), Non Otti Securities Adjustment, After Tax	(361,000,000)	238,000,000	(768,000,000)
Net unrealized gains (losses) on non-OTTI securities, after-tax, Ending Balance	286,000,000	647,000,000	409,000,000
Net Unrealized Gains Losses On Otti Securities [Abstract]
Net unrealized gains (losses) on OTTI securities, after tax, Beginning Balance	74,000,000	24,000,000	(123,000,000)
Other Comprehensive Income Loss Otti Securities Adjustment After Tax	(8,000,000)	50,000,000	147,000,000
Net unrealized gains (losses) on OTTI securities, after tax, Ending Balance	66,000,000	74,000,000	24,000,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax [Abstract]
Net unrealized gains (losses) on cash flow hedge derivatives, after-tax, Beginning balance	350,000,000	243,000,000	578,000,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	80,000,000	107,000,000	(335,000,000)
Net unrealized gains (losses) on cash flow hedge derivatives, after-tax, Ending balance	430,000,000	350,000,000	243,000,000
Pension and other postretirement benefit plan adjustments [Abstract]
Pension and other postretirement benefit plan adjustments, after tax, Beginning Balance	(520,000,000)	(237,000,000)	(777,000,000)
Pension and other postretirement benefit plan adjustments, net activity, After Tax	(34,000,000)	(283,000,000)	540,000,000
Pension and other postretirement benefit plan adjustments, after tax, Ending Balance	(554,000,000)	(520,000,000)	(237,000,000)
Other Comprehensive Income Other Adjustments [Abstract]
Other, after tax, Beginning balance	(48,000,000)	(3,000,000)	(21,000,000)
Total Other, net activity, After tax	(50,000,000)	(45,000,000)	18,000,000
Other, after tax, Ending balance	(98,000,000)	(48,000,000)	(3,000,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	503,000,000	436,000,000	834,000,000
Other comprehensive income (loss), after tax and net of reclassifications into Net income	(373,000,000)	67,000,000	(398,000,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ 130,000,000	$ 503,000,000	$ 436,000,000