Changes in Accumulated Other Comprehensive Loss - Foreign Currency Translation Adjustment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in other comprehensive income
Beginning balance	$ 2,587	$ 2,196	$ 1,871
Net change in accumulated other comprehensive loss	(12)	(27)	(62)
Ending balance	2,895	2,587	2,196
Foreign Currency Translation Adjustment [Member]
Changes in other comprehensive income
Beginning balance	(1,087)	(1,060)	(998)
Net translation on investments in foreign operations	119	17	(189)
Net hedges of investments in foreign operations			127
Net hedges of investments in foreign operations	(131)	(44)	127
Net change in accumulated other comprehensive loss	(12)	(27)	(62)
Ending balance	$ (1,099)	$ (1,087)	$ (1,060)