Summary of Deferred Revenue (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 7,973	$ 7,716
Fixed-Price Projects
Deferred Revenue Arrangement [Line Items]
Deferred revenue	5,216	6,859
Other Deferred Revenue
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 2,757	$ 857