- Change in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	$ 16,580	$ 18,355
Other comprehensive income (loss) before reclassifications	159	(254)
Other Comprehensive Income (Loss), Net of Tax	183	(241)
Amounts reclassified from AOCI	24	13
Balance, ending	16,964	18,293
Adjustments to Additional Paid in Capital, Other		(21)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	(220)	(174)
Other comprehensive income (loss) before reclassifications	10	(58)
Amounts reclassified from AOCI	14	0
Balance, ending	(196)	(232)
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	(373)	(233)
Other comprehensive income (loss) before reclassifications	148	(193)
Amounts reclassified from AOCI	4	3
Balance, ending	(221)	(423)
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	(19)
Other comprehensive income (loss) before reclassifications		(2)
Other Comprehensive Income (Loss), Net of Tax	0
Amounts reclassified from AOCI	0	0
Balance, ending	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	(730)	(600)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI	6	10
Balance, ending	(724)	(590)
Adjustments to Additional Paid in Capital, Other		0
Accumulated Other
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	(1)	0
Other comprehensive income (loss) before reclassifications	1	(1)
Amounts reclassified from AOCI	0	0
Balance, ending	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	(1,324)	(1,026)
Other Comprehensive Income (Loss), Net of Tax	183	(241)
Balance, ending	$ (1,141)	$ (1,246)