| Goodwill and Intangible Assets (Tables)
 | 12 Months Ended | 
| Dec. 31, 2016 | 
|---|
| Goodwill and Intangible Assets Disclosure [Abstract] |  | 
| Goodwill by Operating Segment | 
Changes in goodwill for the years ended December 31, 2016 and 2015 are as follows (in thousands):
 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Supply Chain Management |   | IT, Energy and Management Consulting |   | Aviation |   | Total |  
| Balance as of December 31, 2014 | $ | 61,169 | 
 |   | $ | 30,883 | 
 |   | $ | — | 
 |   | $ | 92,052 | 
 |  
| Increase from acquisitions | 1,944 | 
 |   | — | 
 |   | 104,549 | 
 |   | 106,493 | 
 |  
| Balance as of December 31, 2015 | $ | 63,113 | 
 |   | $ | 30,883 | 
 |   | $ | 104,549 | 
 |   | $ | 198,545 | 
 |  
| Increase from acquisitions | 77 | 
 |   | — | 
 |   | — | 
 |   | 77 | 
 |  
| Balance as of December 31, 2016 | $ | 63,190 | 
 |   | $ | 30,883 | 
 |   | $ | 104,549 | 
 |   | $ | 198,622 | 
 |  | 
| Intangible Assets | 
Intangible assets were composed of the following (in thousands): 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Cost |   | Accumulated Amortization |   | Accumulated Impairment Loss |   | Net Intangible Assets |  
| December 31, 2016 |   |   |   |   |   |   |   |  
| Contract and customer-related | $ | 173,094 | 
 |   | $ | (59,799 | ) |   | $ | (1,025 | ) |   | $ | 112,270 | 
 |  
| Acquired technologies | 12,400 | 
 |   | (6,278 | ) |   | — | 
 |   | 6,122 | 
 |  
| Trade names | 16,670 | 
 |   | (8,136 | ) |   | — | 
 |   | 8,534 | 
 |  
| Total | $ | 202,164 | 
 |   | $ | (74,213 | ) |   | $ | (1,025 | ) |   | $ | 126,926 | 
 |  
|   |   |   |   |   |   |   |   |  
| December 31, 2015 |   | 
 |   |   | 
 |   |   | 
 |   |   | 
 |  
| Contract and customer-related | $ | 173,084 | 
 |   | $ | (46,611 | ) |   | $ | (1,025 | ) |   | $ | 125,448 | 
 |  
| Acquired technologies | 12,400 | 
 |   | (5,151 | ) |   | — | 
 |   | 7,249 | 
 |  
| Trade names | 16,730 | 
 |   | (6,384 | ) |   | — | 
 |   | 10,346 | 
 |  
| Total | $ | 202,214 | 
 |   | $ | (58,146 | ) |   | $ | (1,025 | ) |   | $ | 143,043 | 
 |  | 
| Future Amortization of Intangible Assets | 
Future expected amortization of intangible assets is as follows for the years ending December 31, (in thousands): 
|  |  
|  |  |  |  |  
|   | Amortization |  
| 2017 | $ | 16,017 | 
 |  
| 2018 | 16,017 | 
 |  
| 2019 | 15,953 | 
 |  
| 2020 | 15,362 | 
 |  
| 2021 | 14,998 | 
 |  
| Thereafter | 48,579 | 
 |  
| Total | $ | 126,926 | 
 |  |