Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts - 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	$ 25	$ 25	$ 25
Additions charged to expense	25	3	5
Deductions/other	(12)	(3)	(5)
Balance at end of year	$ 38	$ 25	$ 25