Costs and Estimated Earnings on Uncompleted Contracts - Summary of Costs and Estimated Earnings on Uncompleted Contracts (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Contracts In Progress Costs And Earnings [Line Items]
Costs and estimated earnings on uncompleted contracts	$ 33,414	$ 22,524
Cost Incurred on Uncompleted Contracts [Member]
Contracts In Progress Costs And Earnings [Line Items]
Costs and estimated earnings on uncompleted contracts	80,145	55,349
Estimated Earnings [Member]
Contracts In Progress Costs And Earnings [Line Items]
Costs and estimated earnings on uncompleted contracts	30,696	20,883
Billings to Date [Member]
Contracts In Progress Costs And Earnings [Line Items]
Costs and estimated earnings on uncompleted contracts	$ 77,427	$ 53,708