Schedule II Valuation and Qualifying Accounts (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020
Valuation And Qualifying Accounts Disclosure [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201602Member	us-gaap:AccountingStandardsUpdate201409Member
Retained earnings	$ 4,809	$ 6,113
Accounts receivable	1,691	1,941
Deferred income taxes	$ 1,467	$ 1,527
Accounting Standards Update 2016-13 | Restatement Adjustment
Valuation And Qualifying Accounts Disclosure [Line Items]
Retained earnings				$ (12)
Accounts receivable				(15)
Deferred income taxes				$ 3