Accumulated Other Comprehensive Income Reclassifications out of AOCI (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax		$ (14)	$ 1	$ (14)	$ 2
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax		5	(1)	5	(1)
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax		(9)	0	(9)	1
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax		(63)	(101)	(117)	(203)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Tax		24	37	44	75
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax		(39)	(64)	(73)	(128)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Tax		4	3	(112)	51
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax		2	(1)	45	(19)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		6	2	(67)	32
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		42	62	149	95
Other Assets And Liabilities, Net [Member]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Tax	[1]	0	0	(120)	46
Amortization of Actuarial Loss [Member]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Tax		6	4	11	8
Amortization of Prior Service Credit [Member]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Tax		$ (2)	$ (1)	$ (3)	$ (3)

[1] For additional information on the funded status of the pension and other postretirement benefits plans, see Note 15, "Employee Benefit Plans," to the Company's 2014 Annual Report on Form 10-K.