Accumulated Other Comprehensive Loss (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Change in accumulated other comprehensive loss balances:
Beginning Balance	$ (513)	$ (597)	$ (752)	$ (729)
Other comprehensive income (loss) before reclassifications	157	(54)	420	86
Amounts reclassified from AOCI	30	(15)	(54)	(23)
Ending Balance	(386)	(666)	(386)	(666)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Change in accumulated other comprehensive loss balances:
Beginning Balance	171	73	36	21
Other comprehensive income (loss) before reclassifications	88	(5)	249	67
Amounts reclassified from AOCI	(27)	(25)	(53)	(45)
Ending Balance	232	43	232	43
Net Unrealized Gains (Losses) on Securities
Change in accumulated other comprehensive loss balances:
Beginning Balance	(60)	(72)	(151)	(145)
Other comprehensive income (loss) before reclassifications	67	(51)	166	24
Amounts reclassified from AOCI	(12)	(3)	(20)	(5)
Ending Balance	(5)	(126)	(5)	(126)
Foreign Currency Translation Adjustment
Change in accumulated other comprehensive loss balances:
Beginning Balance	(21)	(17)	(25)	(10)
Other comprehensive income (loss) before reclassifications	1	2	5	(5)
Amounts reclassified from AOCI	0	0	0	0
Ending Balance	(20)	(15)	(20)	(15)
Pension and Other Benefits Adjustment
Change in accumulated other comprehensive loss balances:
Beginning Balance	(602)	(581)	(612)	(595)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from AOCI	9	13	19	27
Ending Balance	(593)	(568)	(593)	(568)
Accumulated Other [Member]
Change in accumulated other comprehensive loss balances:
Beginning Balance	(1)	0
Other comprehensive income (loss) before reclassifications	1	0
Amounts reclassified from AOCI	0	0
Ending Balance	$ 0	$ 0	$ 0	$ 0