Revenue (Components of Contracts in Progress) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings in excess of billings for contracts in progress	$ 27,227	$ 18,546
Costs and earnings in excess of billings for completed contracts	11,965	6,126
Total contract revenues in excess of billings	39,192	24,672
Current portion of contract revenues in excess of billings	37,080	22,560
Long-term contract revenues in excess of billings	2,112	2,112
Total billings in excess of contract revenues	(61,327)	(55,266)
Costs And Earnings In Excess Of Billings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	327,616	104,620
Amounts billed	(300,389)	(86,074)
Billings In Excess Of Costs And Earnings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	394,515	573,225
Amounts billed	$ (455,842)	$ (628,491)