Annual report pursuant to Section 13 and 15(d)

Business Segment Information - Additional Information (Details)

v3.10.0.1
Business Segment Information - Additional Information (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Segment Reporting Information [Line Items]      
Unallocated corporate expense segment $ (30,415) $ (27,195) $ (32,225)
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% 77.00% 77.00%
U.S. Federal Government | Sales Revenue, Net | Customer Concentration Risk      
Segment Reporting Information [Line Items]      
Concentration risk percentage 31.30% 32.00% 27.30%
Canada | Operating Segments      
Segment Reporting Information [Line Items]      
Interest and debt expense     $ 1,934