Accounts Receivable, Net - Provision for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 282	$ 324
Accounts receivable, provision for credit loss, period increase	18	4
Accounts receivable, provision for credit loss, writeoff	(23)	(17)
Accounts receivable, provision for credit loss, recovery	0	1
Accounts receivable, provision for credit loss, foreign exchange	(6)	1
Ending balance	$ 271	$ 313