Accounts Receivable And Contracts In Progress (Components Of Contracts In Progress) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings in excess of billings for contracts in progress	$ 53,778	$ 75,823
Costs and earnings in excess of billings for completed contracts	21,918	19,189
Total contract revenues in excess of billings	75,696	95,012
Total billings in excess of contract revenues	(8,893)	(5,141)
Costs And Earnings In Excess Of Billings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	553,027	587,371
Amounts billed	(499,249)	(511,548)
Billings In Excess Of Costs And Earnings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	332,107	263,613
Amounts billed	$ (341,000)	$ (268,754)