Summary Of Major Accounting Policies - Percentage-of-Completion (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Temporary Differences Using Percentage of Completion [Line Items]
Revenue Recognition, Multiple-deliverable Arrangements, Percentage of Revenue Accounted Under the Percentage of Completion Method	20.00%
Contract in Unbilled Receivable Position [Member]
Schedule Temporary Differences Using Percentage of Completion [Line Items]
Fixed-price Contract, Percentage of Completion, Revenue Recognized to Date	$ 349,233	$ 538,986
Billed Contracts Receivable	(309,355)	(488,814)
Costs in Excess of Billings on Uncompleted Contracts or Programs	39,878	50,172
Contracts in Unearned Revenue Position [Member]
Schedule Temporary Differences Using Percentage of Completion [Line Items]
Fixed-price Contract, Percentage of Completion, Revenue Recognized to Date	(111,330)	(81,800)
Billed Contracts Receivable	145,258	178,914
Billings in Excess of Cost	$ 33,928	$ 97,114

Fixed-price Contract, Percentage of Completion, Revenue Recognized to Date

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Revenue Recognition, Multiple-deliverable Arrangements, Percentage of Revenue Accounted Under the Percentage of Completion Method

+ References

No definition available.

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Schedule Temporary Differences Using Percentage of Completion [Line Items]

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Amounts due for billed services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the Company and, at a minimum, one other party. An example would be amounts billed to customers under contracts or programs but not paid as of the balance sheet date.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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Liability attributable to (i) billings in excess of costs under the percentage of completion contract accounting method representing the difference between contractually invoiced amounts (billings) and revenue recognized based, for example, on costs incurred to estimated total costs at period end or (ii) contractually invoiced amounts (billings) in excess of costs incurred and accumulated under the completed contract accounting method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 35
-Section 45
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Amount of receivable reflecting the cost incurred on uncompleted contracts in excess of related billings.

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-Publisher FASB
-Name Accounting Standards Codification
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