- Change in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	$ 16,737	$ 17,329	$ 16,367	$ 16,580
Other comprehensive income (loss) before reclassifications			916	440
Other Comprehensive Income (Loss), Net of Tax	48	110	876	501
Amounts reclassified from AOCI			(40)	61
Balance, ending	16,941	16,100	16,941	16,100
Adjustments to Additional Paid in Capital, Other	(19)	(18)	3	3
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	245	(140)	(115)	(220)
Other comprehensive income (loss) before reclassifications	0	30	352	81
Amounts reclassified from AOCI	(15)	20	(7)	49
Balance, ending	230	(90)	230	(90)
Net Unrealized Gains (Losses) on Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	344	(75)	(93)	(373)
Other comprehensive income (loss) before reclassifications	58	53	564	358
Amounts reclassified from AOCI	(11)	0	(80)	(7)
Balance, ending	391	(22)	391	(22)
Foreign Currency Translation Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	0	0	0	0
Other comprehensive income (loss) before reclassifications	0	0		0
Other Comprehensive Income (Loss), Net of Tax			0
Amounts reclassified from AOCI	0	0	0	0
Balance, ending	0	0	0	0
Pension and Other Benefits Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	(623)	(718)	(654)	(730)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from AOCI	16	7	47	19
Balance, ending	(607)	(711)	(607)	(711)
Accumulated Other
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	0	0	0	(1)
Other comprehensive income (loss) before reclassifications	0	0	0	1
Amounts reclassified from AOCI	0	0	0	0
Balance, ending	0	0	0	0
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning	(34)	(933)	(862)	(1,324)
Other comprehensive income (loss) before reclassifications	58	83
Other Comprehensive Income (Loss), Net of Tax	48	110	876	501
Amounts reclassified from AOCI	(10)	27
Balance, ending	$ 14	$ (823)	$ 14	$ (823)