Receivables, Net - Summary of Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable-gross	$ 368,754	$ 473,757	$ 330,297
Less: allowance for doubtful accounts	539	511	105
Accounts receivable-net	368,215	473,246	330,192
Completed and in Progress [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Billed	200,908	285,521	214,494
Unbilled	112,892	98,755	73,128
Accounts receivable-gross	313,800	384,276	287,622
Material Sales [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable-gross	29,948	45,286	28,233
Other Business Products and Services [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable-gross	$ 25,006	$ 44,195	$ 14,442