Accumulated Other Comprehensive Income (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Change in accumulated other comprehensive loss balances:
Beginning Balance			$ 17,233
Ending Balance	$ 17,808		17,808
Net Unrealized Gains (Losses) on Cash Flow Hedges
Change in accumulated other comprehensive loss balances:
Beginning Balance	(107)	$ 170	(77)	$ 38
Other comprehensive income (loss) before reclassifications	34	85	22	243
Amounts reclassified from AOCI	(12)	(27)	(30)	(53)
Ending Balance	(85)	228	(85)	228
Net Unrealized Gains (Losses) on Securities
Change in accumulated other comprehensive loss balances:
Beginning Balance	(173)	(62)	(208)	(152)
Other comprehensive income (loss) before reclassifications	26	67	59	164
Amounts reclassified from AOCI	(2)	(11)	0	(18)
Ending Balance	(149)	(6)	(149)	(6)
Foreign Currency Translation Adjustment
Change in accumulated other comprehensive loss balances:
Beginning Balance	(21)	(20)	(22)	(24)
Other comprehensive income (loss) before reclassifications	2	1	3	5
Amounts reclassified from AOCI	0	0	0	0
Ending Balance	(19)	(19)	(19)	(19)
Pension and Other Benefits Adjustment
Change in accumulated other comprehensive loss balances:
Beginning Balance	(582)	(602)	(589)	(612)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from AOCI	6	9	13	19
Ending Balance	(576)	(593)	(576)	(593)
Accumulated Other
Change in accumulated other comprehensive loss balances:
Beginning Balance	0	(2)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI	0	2
Ending Balance	0	0	0	0
Accumulated Other Comprehensive Loss
Change in accumulated other comprehensive loss balances:
Beginning Balance	(883)	(516)	(896)	(750)
Other comprehensive income (loss) before reclassifications	62	153	84	412
Amounts reclassified from AOCI	(8)	(27)	(17)	(52)
Ending Balance	$ (829)	$ (390)	$ (829)	$ (390)