Accumulated Other Comprehensive Loss (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Change in accumulated other comprehensive loss balances:
Beginning Balance	$ (597)	$ (559)	$ (729)	$ (624)
Other comprehensive income (loss) before reclassifications	(54)	137	86	210
Amounts reclassified from AOCI	(15)	(19)	(23)	(27)
Ending Balance	(666)	(441)	(666)	(441)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Change in accumulated other comprehensive loss balances:
Beginning Balance	73	7	21	16
Other comprehensive income (loss) before reclassifications	(5)	42	67	47
Amounts reclassified from AOCI	(25)	(17)	(45)	(31)
Ending Balance	43	32	43	32
Net Unrealized Gains (Losses) on Securities
Change in accumulated other comprehensive loss balances:
Beginning Balance	(72)	(260)	(145)	(328)
Other comprehensive income (loss) before reclassifications	(51)	95	24	165
Amounts reclassified from AOCI	(3)	(8)	(5)	(10)
Ending Balance	(126)	(173)	(126)	(173)
Foreign Currency Translation Adjustment
Change in accumulated other comprehensive loss balances:
Beginning Balance	(17)	(5)	(10)	(3)
Other comprehensive income (loss) before reclassifications	2	2	(5)	0
Amounts reclassified from AOCI	0	0	0	0
Ending Balance	(15)	(3)	(15)	(3)
Pension and Other Benefits Adjustment
Change in accumulated other comprehensive loss balances:
Beginning Balance	(581)	(301)	(595)	(309)
Other comprehensive income (loss) before reclassifications	0	(2)	0	(2)
Amounts reclassified from AOCI	13	6	27	14
Ending Balance	$ (568)	$ (297)	$ (568)	$ (297)