Goodwill and Other Intangible Assets (Schedule of Other Intangible Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 484,575	$ 485,237
Accumulated Amortization	289,223	283,006
Net Carrying Amount	195,352	202,231
Contract and program intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	430,632	430,632
Accumulated Amortization	247,188	242,194
Net Carrying Amount	183,444	188,438
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	53,943	54,605
Accumulated Amortization	42,035	40,812
Net Carrying Amount	$ 11,908	$ 13,793