Other Financial Data - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 84	$ 65	$ 70	$ 64
Provision	4	7	19	19
Accounts written off, net of recoveries	0	(6)	(11)	(17)
Foreign currency translation and other	1	1	4	1
Balance at end of period	89	67	89	67
Cumulative adjustment amount to decrease retained earnings	(3,620)	(3,561)	(3,620)	(3,561)	$ (3,695)	$ (3,260)		$ (3,449)	$ (3,913)	$ (4,862)	$ (4,219)
Retained Earnings
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Cumulative adjustment amount to decrease retained earnings	(1,423)	(1,436)	(1,423)	(1,436)	$ (1,751)	$ (1,455)		(1,254)	$ (1,669)	$ (2,555)	$ (2,093)
Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	0	0	7	0
Cumulative adjustment amount to decrease retained earnings								6
Cumulative Effect, Period Of Adoption, Adjustment | Retained Earnings
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Cumulative adjustment amount to decrease retained earnings							$ 6	6
Cumulative Effect, Period Of Adoption, Adjusted Balance
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 84	$ 65	$ 77	$ 64
Cumulative adjustment amount to decrease retained earnings								(3,443)
Cumulative Effect, Period Of Adoption, Adjusted Balance | Retained Earnings
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Cumulative adjustment amount to decrease retained earnings								$ (1,248)