Contract Balances - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Contract With Customer Asset And Liability [Line Items]
Bad debt expense and write-offs (reversals)	$ 800,000	$ 200,000
Revenue, Remaining performance obligation	194,600,000
Prepaid Expenses and Other Current Assets
Contract With Customer Asset And Liability [Line Items]
Assets impairment charges	0	0
Contract assets	1,200,000		$ 800,000
Current Deferred Revenue and Advanced Payments
Contract With Customer Asset And Liability [Line Items]
Revenue recognized from beginning deferred revenue	$ 67,000,000	$ 74,600,000