Quarterly report pursuant to Section 13 or 15(d)

Revenue - Disaggregation of Revenue (Details)

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Revenue - Disaggregation of Revenue (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Disaggregation of Revenue [Line Items]        
Revenues $ 168,931 $ 174,164 $ 516,222 $ 565,318
Cost-type        
Disaggregation of Revenue [Line Items]        
Revenues 44,638   138,658  
Fixed-price        
Disaggregation of Revenue [Line Items]        
Revenues 91,220   273,063  
Time and materials        
Disaggregation of Revenue [Line Items]        
Revenues 33,073   104,501  
U.S. Postal Service        
Disaggregation of Revenue [Line Items]        
Revenues 43,031 43,833 130,151 136,261
DoD        
Disaggregation of Revenue [Line Items]        
Revenues 80,002   249,842  
Commercial        
Disaggregation of Revenue [Line Items]        
Revenues 36,027 33,470 108,631 103,976
Other government        
Disaggregation of Revenue [Line Items]        
Revenues 9,871 $ 9,282 27,598 $ 25,636
Supply Chain Management        
Disaggregation of Revenue [Line Items]        
Revenues 51,834   161,961  
Supply Chain Management | Cost-type        
Disaggregation of Revenue [Line Items]        
Revenues 0   0  
Supply Chain Management | Fixed-price        
Disaggregation of Revenue [Line Items]        
Revenues 51,834   161,961  
Supply Chain Management | Time and materials        
Disaggregation of Revenue [Line Items]        
Revenues 0   0  
Supply Chain Management | U.S. Postal Service        
Disaggregation of Revenue [Line Items]        
Revenues 43,031   130,151  
Supply Chain Management | DoD        
Disaggregation of Revenue [Line Items]        
Revenues 5,479   21,180  
Supply Chain Management | Commercial        
Disaggregation of Revenue [Line Items]        
Revenues 3,324   10,123  
Supply Chain Management | Other government        
Disaggregation of Revenue [Line Items]        
Revenues 0   507  
Aviation        
Disaggregation of Revenue [Line Items]        
Revenues 34,000   102,554  
Aviation | Cost-type        
Disaggregation of Revenue [Line Items]        
Revenues 0   1,098  
Aviation | Fixed-price        
Disaggregation of Revenue [Line Items]        
Revenues 20,152   59,525  
Aviation | Time and materials        
Disaggregation of Revenue [Line Items]        
Revenues 13,848   41,931  
Aviation | U.S. Postal Service        
Disaggregation of Revenue [Line Items]        
Revenues 0   0  
Aviation | DoD        
Disaggregation of Revenue [Line Items]        
Revenues 913   3,153  
Aviation | Commercial        
Disaggregation of Revenue [Line Items]        
Revenues 32,641   98,213  
Aviation | Other government        
Disaggregation of Revenue [Line Items]        
Revenues 446   1,188  
Federal Services Group        
Disaggregation of Revenue [Line Items]        
Revenues 83,097   251,707  
Federal Services Group | Cost-type        
Disaggregation of Revenue [Line Items]        
Revenues 44,638   137,560  
Federal Services Group | Fixed-price        
Disaggregation of Revenue [Line Items]        
Revenues 19,234   51,577  
Federal Services Group | Time and materials        
Disaggregation of Revenue [Line Items]        
Revenues 19,225   62,570  
Federal Services Group | U.S. Postal Service        
Disaggregation of Revenue [Line Items]        
Revenues 0   0  
Federal Services Group | DoD        
Disaggregation of Revenue [Line Items]        
Revenues 73,610   225,509  
Federal Services Group | Commercial        
Disaggregation of Revenue [Line Items]        
Revenues 62   295  
Federal Services Group | Other government        
Disaggregation of Revenue [Line Items]        
Revenues $ 9,425   $ 25,903