Valuation and Qualifying Accounts - Summary of Activity for Valuation Allowances (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance, Accounts receivable allowance	$ (20)	$ (20)	$ (20)	$ (14)
Charged to costs and expenses, Accounts receivable allowance		(26)	(10)	(15)
Deductions, Accounts receivable allowance		14	10	9
Ending balance, Accounts receivable allowance		(34)	(20)	(20)	$ (14)
Beginning balance, Deferred tax assets valuation allowance	$ (5)	(9)	(5)	(6)
Charged to costs and expenses, Deferred tax assets valuation allowance		(6)	(4)	0
Deductions, Deferred tax assets valuation allowance		0	0	1
Ending balance, Deferred tax assets valuation allowance		(15)	$ (9)	$ (5)	$ (6)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member		us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201802Member
Cumulative Effect, Period of Adoption, Adjustment
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance, Accounts receivable allowance		$ 2
Ending balance, Accounts receivable allowance			$ 2
Accounting Standards Update [Extensible List]				us-gaap:AccountingStandardsUpdate201802Member	us-gaap:AccountingStandardsUpdate201602Member