Goodwill and Other Intangible Assets (Schedule of Other Intangible Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 485,203	$ 485,237
Accumulated Amortization	296,121	283,006
Net Carrying Amount	189,082	202,231
Contract and program intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	430,632	430,632
Accumulated Amortization	252,191	242,194
Net Carrying Amount	178,441	188,438
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	54,571	54,605
Accumulated Amortization	43,930	40,812
Net Carrying Amount	$ 10,641	$ 13,793