Equity - Accumulated Other Comprehensive 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]
Beginning Balance	$ 17,493	$ 34,664	$ 34,414	$ 34,876
Other comprehensive loss before reclassifications			(164)	(116)
Amounts reclassified from accumulated other comprehensive income (loss)			33	21
Deferred taxes			(2)	(4)
Other comprehensive income (loss)	83	(115)	(133)	(99)
Less: Other comprehensive loss attributable to noncontrolling interests	0	0	(3)	(1)
Less: Other adjustments			0	119
Ending Balance	17,140	34,343	17,140	34,343
Investment Securities, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			2	0
Ending Balance	0	0	0	0
Investment Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive loss before reclassifications			(2)	0
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Deferred taxes			0	0
Other comprehensive income (loss)			(2)	0
Investment Securities, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive loss attributable to noncontrolling interests			0	0
Less: Other adjustments			0	0
Foreign Currency Translation Adjustment, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			(2,274)	(2,326)
Ending Balance	(2,371)	(2,421)	(2,371)	(2,421)
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive loss before reclassifications			(101)	(96)
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Deferred taxes			0	0
Other comprehensive income (loss)			(101)	(96)
Foreign Currency Translation Adjustments, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive loss attributable to noncontrolling interests			(3)	(1)
Less: Other adjustments			(1)	0
Cash Flow Hedges, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			10	(3)
Ending Balance	4	0	4	0
Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive loss before reclassifications			(5)	2
Amounts reclassified from accumulated other comprehensive income (loss)			(2)	2
Deferred taxes			1	(1)
Other comprehensive income (loss)			(6)	3
Cash Flow Hedges, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive loss attributable to noncontrolling interests			0	0
Less: Other adjustments			0	0
Benefit Plans, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			(327)	(133)
Ending Balance	(352)	(258)	(352)	(258)
Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive loss before reclassifications			(56)	(22)
Amounts reclassified from accumulated other comprehensive income (loss)			35	19
Deferred taxes			(3)	(3)
Other comprehensive income (loss)			(24)	(6)
Benefit Plans, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive loss attributable to noncontrolling interests			0	0
Less: Other adjustments			1	119
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(2,802)	(2,564)	(2,589)	(2,462)
Other comprehensive income (loss)	83	(115)	(130)	(98)
Ending Balance	$ (2,719)	$ (2,679)	$ (2,719)	$ (2,679)