Business Segment Information - Additional Information (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Segment Reporting Information [Line Items] | |||
| Unallocated corporate expense segment | $ (27,195) | $ (32,225) | $ (26,077) |
| Customer Who Declared Bankruptcy | |||
| Segment Reporting Information [Line Items] | |||
| Unallocated corporate expense segment | $ 2,870 | ||
| Various Governments | Sales Revenue, Net | Customer Concentration Risk | |||
| Segment Reporting Information [Line Items] | |||
| Concentration risk percentage | 77.00% | 75.00% | 75.00% |
| U.S. Federal Government | Sales Revenue, Net | Customer Concentration Risk | |||
| Segment Reporting Information [Line Items] | |||
| Concentration risk percentage | 32.00% | 27.30% | 20.20% |
| Canada | Operating Segments | |||
| Segment Reporting Information [Line Items] | |||
| Interest and debt expense | $ 1,934 | $ 1,934 | |
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- Definition Unallocated Corporate Expense Segment No definition available.
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- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Interest and debt related expenses associated with nonoperating financing activities of the entity. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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