Revenue (Components of Contracts in Progress) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings in excess of billings for contracts in progress	$ 18,546	$ 16,137
Costs and earnings in excess of billings for completed contracts	6,126	3,928
Total contract revenues in excess of billings	24,672	20,065
Current portion of contract revenues in excess of billings	22,560	17,953
Long-term contract revenues in excess of billings	2,112	2,112
Total billings in excess of contract revenues	(55,266)	(17,793)
Costs And Earnings In Excess Of Billings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	104,620	433,093
Amounts billed	(86,074)	(416,956)
Billings In Excess Of Costs And Earnings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	573,225	242,898
Amounts billed	$ (628,491)	$ (260,691)