Basis of Presentation and Summary of Significant Accounting Policies - Summary of Estimated Revenue Expected to be Recognized Over Time Related to Performance Obligations (Detail) $ in Thousands	Jun. 30, 2018 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue remaining performance obligation, remainder of 2018	$ 88,060
Revenue remaining performance obligation, 2019	57,418
Revenue remaining performance obligation, 2020	21,854
Revenue remaining performance obligation, 2021	6,011
Revenue remaining performance obligation, Thereafter	1,308
Performance Obligations Transferred Over Time [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue remaining performance obligation, remainder of 2018	88,060
Revenue remaining performance obligation, 2019	57,418
Revenue remaining performance obligation, 2020	21,854
Revenue remaining performance obligation, 2021	6,011
Revenue remaining performance obligation, Thereafter	$ 1,308