Schedule of Estimated Revenue Expected to be Recognized in Future Related to Performance Obligations (Detail) $ in Thousands	Jun. 30, 2018 USD ($)
Remainder of 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue remaining performance obligation	$ 4,215
2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue remaining performance obligation	5,630
2020
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue remaining performance obligation	3,000
2021
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue remaining performance obligation	$ 1,500