Schedule of Estimated Revenue Expected to be Recognized in Future Related to Performance Obligations (Detail) $ in Thousands	Mar. 31, 2018 USD ($)
Remainder of 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue remaining performance obligation	$ 7,340
2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue remaining performance obligation	5,067
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