Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] $ in Thousands	Jun. 30, 2018 USD ($)
Assets
Total assets	$ 15,330
Cash [Member]
Assets
Total assets	1,083
Money market securities (cash equivalents) [Member]
Assets
Total assets	14,197
Restricted cash [Member]
Assets
Total assets	50
Level 1 [Member]
Assets
Total assets	15,330
Level 1 [Member] | Cash [Member]
Assets
Total assets	1,083
Level 1 [Member] | Money market securities (cash equivalents) [Member]
Assets
Total assets	14,197
Level 1 [Member] | Restricted cash [Member]
Assets
Total assets	$ 50