Description of Business, Accounting Policies, and Supplemental Disclosures - Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Liability for return allowance	$ 859	$ 712	$ 623
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Rights to recover products from customers	852	629	519
Sales Returns and Allowances
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Additions to allowance for returns	3,500	2,500	2,300
Deductions to allowance for returns	$ 3,600	$ 2,500	$ 2,300