Schedule II: Valuation and Qualifying Accounts (Details) - Allowance for doubtful accounts and sales credits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 753	$ 729	$ 674
Additions	2,013	1,481	1,115
Usage	(1,422)	(1,457)	(1,060)
Balance at End of Year	$ 1,344	$ 753	$ 729