Summary of Significant Accounting Policies - Summary of Allowance for Doubtful Accounts Activity (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Allowance for doubtful accounts, Beginning Balance	$ 1,920	$ 2,087
Provision for doubtful accounts	581	1,480	$ 1,892
Write-offs, net of recoveries	(618)	(1,647)
Allowance for doubtful accounts, Ending Balance	$ 1,883	$ 1,920	$ 2,087