Leases-Balance Sheet Classification and Other Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Balance Sheet Classification [Abstract]
Long-term lease liabilities	$ 5,596	$ 0
Total operating lease liabilities	$ 7,583
Other Information [Abstract]
Weighted-average remaining term for operating leases	6 years 7 months 6 days
Weighted -average discount rate for operating leases	8.74%
Accounts Payable and Accrued Liabilities [Member]
Balance Sheet Classification [Abstract]
Current lease liabilities (recorded in accrued expenses and other current liabilities)	$ 1,987