Income Taxes - Components of Company's Income Tax Provision (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense:
Federal			$ 0	$ 0	$ 0
State			(42)	185	161
Foreign			347	(9)	264
Total			305	176	425
Deferred tax expense (benefit):
Federal			6,825	801	(544)
State			(1,016)	344	476
Foreign				9	205
Change in valuation allowance	$ (22,000)	$ (3,700)	13,526	3,700	3,000
Total			19,335	4,854	3,137
Unrecognized tax benefit			(25)		(33)
Income tax provision			$ 19,615	$ 5,030	$ 3,529