- Change in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	$ 16,964	$ 18,293	$ 16,580	$ 18,355
Other comprehensive income (loss) before reclassifications			357	(313)
Other Comprehensive Income (Loss), Net of Tax	208	(39)	391	(280)
Amounts reclassified from AOCI			34	33
Balance, ending	17,329	18,547	17,329	18,547
Adjustments to Additional Paid in Capital, Other	38	37	21	23
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	(196)	(232)	(220)	(174)
Other comprehensive income (loss) before reclassifications	41	(14)	51	(72)
Amounts reclassified from AOCI	15	6	29	6
Balance, ending	(140)	(240)	(140)	(240)
Adjustments to Additional Paid in Capital, Other				0
Net Unrealized Gains (Losses) on Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	(221)	(423)	(373)	(233)
Other comprehensive income (loss) before reclassifications	157	(45)	305	(238)
Amounts reclassified from AOCI	(11)	4	(7)	7
Balance, ending	(75)	(464)	(75)	(464)
Adjustments to Additional Paid in Capital, Other				0
Foreign Currency Translation Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	0	0	0	(19)
Other comprehensive income (loss) before reclassifications	0	0		(2)
Other Comprehensive Income (Loss), Net of Tax			0
Amounts reclassified from AOCI	0	0	0	0
Balance, ending	0	0	0	0
Adjustments to Additional Paid in Capital, Other				21
Pension and Other Benefits Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	(724)	(590)	(730)	(600)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from AOCI	6	10	12	20
Balance, ending	(718)	(580)	(718)	(580)
Adjustments to Additional Paid in Capital, Other				0
Accumulated Other
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	0	(1)	(1)	0
Other comprehensive income (loss) before reclassifications	0	0	1	(1)
Amounts reclassified from AOCI	0	0	0	0
Balance, ending	0	(1)	0	(1)
Adjustments to Additional Paid in Capital, Other				0
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	(1,141)	(1,246)	(1,324)	(1,026)
Other comprehensive income (loss) before reclassifications	198	(59)
Other Comprehensive Income (Loss), Net of Tax	208	(39)	391	(280)
Amounts reclassified from AOCI	10	20
Balance, ending	$ (933)	$ (1,285)	$ (933)	(1,285)
Adjustments to Additional Paid in Capital, Other				$ 21