Receivables - Schedule of Receivables (Details) - USD ($) $ in Thousands |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Receivables [Abstract] | ||
| Billed receivables | $ 102,045 | $ 71,068 |
| Unbilled receivables (contract assets) | 203,127 | 186,365 |
| Other | 9,787 | 11,711 |
| Total Receivables | $ 314,959 | $ 269,144 |