Summary of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Current provision
Federal									$ (110)	$ 204
State									(653)	1,856
Foreign									311
Total current provision									(452)	2,060
Deferred benefit:
Foreign									(240)
Total deferred benefit									(240)
Total current provision	$ (779)	$ (674)	$ 622	$ 139	$ (1,842)	$ 2,011	$ (109)	$ 2,000	$ (692)	$ 2,060