Derivative Instruments - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Derivative [Line Items]
Other Comprehensive Income (Loss), before Tax	$ 875,000,000	$ 858,000,000	$ 859,000,000	$ 3,642,000,000
Derivatives used in Net Investment Hedge, Net of Tax	3,000,000		3,000,000		$ (2,000,000)
Amount of Ineffectiveness on Net Investment Hedges	0		0
Cash flow hedges | Derivatives designated as hedges | Foreign currency swaps
Derivative [Line Items]
Foreign currency swap gains (losses)	(178,000,000)	124,000,000	140,000,000	171,000,000
Foreign currency swap gain (loss) reclassified to income	0	0	0	0
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			0
Fair Value Hedging [Member] | Foreign currency forwards
Derivative [Line Items]
Derivative, Fair Value Hedge, Included in Effectiveness, Gain (Loss)	(2,000,000)	2,000,000	(1,000,000)	1,000,000
Fair Value Hedging [Member] | Derivatives designated as hedges | Foreign currency forwards
Derivative [Line Items]
Derivative, Amount of Hedged Item	1,739,000,000		1,739,000,000		456,000,000
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	60,000,000		60,000,000		$ 1,000,000
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(52,000,000)	13,000,000	(60,000,000)	13,000,000
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	50,000,000	$ (11,000,000)	59,000,000	$ (12,000,000)
Fair Value Hedging [Member] | Derivatives designated as hedges | Net Investment Hedging [Member]
Derivative [Line Items]
Other Comprehensive Income (Loss), before Tax	$ 3,000,000		$ 5,000,000