Derivative Instruments (Hedges of Net Investments in Foreign Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Gains Losses Deferred In Accumulated Other Comprehensive Income Loss On Derivatives	$ (29)	$ (33)	$ 87
Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Gains Losses Deferred In Accumulated Other Comprehensive Income Loss On Derivatives	1	(9)	31
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Gains Losses Deferred In Accumulated Other Comprehensive Income Loss On Derivatives	$ (30)	$ (24)	$ 56