Commitments and Contingencies - Additional Information (Detail) - USD ($)	1 Months Ended	9 Months Ended
	Jul. 31, 2019	Sep. 30, 2021	Dec. 31, 2020
Commitment And Contingencies [Line Items]
Effective date of agreement		Oct. 01, 2017
Purchase amended and restated agreement date	Jul. 01, 2019
Purchase amended and restated agreement effective date	Jan. 01, 2019
Remaining commitments amount		$ 13,000,000	$ 875,000,000
Services Per Year From 2021 Through 2024
Commitment And Contingencies [Line Items]
Commitment to purchase services	$ 184,000,000
Services 2021
Commitment And Contingencies [Line Items]
Commitment to purchase services		45,000,000
Services Per Year From 2022 Through 2025
Commitment And Contingencies [Line Items]
Commitment to purchase services		17,000,000
Services 2025
Commitment And Contingencies [Line Items]
Commitment to purchase services	138,000,000
Commitment
Commitment And Contingencies [Line Items]
Purchase commitment, remaining minimum amount committed	$ 1,400,000,000	$ 90,000,000