Revenue - Summary of Asset Balances and Related Amortization Expense For Contract Costs (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Costs to Obtain a Contract [Member]
Capitalized Contract Cost [Line Items]
Beginning Balance	$ 209,462	$ 178,445	$ 194,964	$ 158,989
Capitalization of Costs	12,174	11,315	41,340	42,513
Amortization	(7,716)	(6,321)	(22,384)	(18,063)
Ending Balance	213,920	183,439	213,920	183,439
Costs to Fulfill a Contract [Member]
Capitalized Contract Cost [Line Items]
Beginning Balance	171,941	121,664	143,788	101,756
Capitalization of Costs	18,709	15,323	57,289	42,614
Amortization	(5,889)	(4,258)	(16,316)	(11,641)
Ending Balance	$ 184,761	$ 132,729	$ 184,761	$ 132,729