Other Financial Data - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020	Dec. 31, 2017
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 70	$ 62	$ 59
Provision	29	27	24
Accounts written off, net of recoveries	(6)	(19)	(25)
Foreign currency translation and other	(2)	0	4
Balance at end of period	98	70	62
Cumulative adjustment amount to decrease retained earnings	(3,583)	(3,449)	(4,219)		$ (4,648)
Retained Earnings
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Cumulative adjustment amount to decrease retained earnings	(1,042)	(1,254)	(2,093)		(2,302)
Cumulative Effect, Period of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7	0	0
Balance at end of period		7	0
Cumulative adjustment amount to decrease retained earnings		6			(492)
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	(493)
Cumulative Effect, Period of Adoption, Adjusted Balance
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 77	62	59
Balance at end of period		77	$ 62
Cumulative adjustment amount to decrease retained earnings		(3,443)			(5,140)
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)			$ (2,795)