Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Goodwill and other intangibles	$ 185,811,000	$ 152,412,000
Property and equipment	22,585,000	17,237,000
Lease arrangements	18,676,000	25,863,000
Unbilled receivables - IRC Section 481(a)	0	2,946,000
Gross deferred tax liabilities	227,072,000	198,458,000
Retirement and other liabilities	(27,575,000)	(23,071,000)
Lease obligations	(21,717,000)	(28,652,000)
Allowance for potential contract losses and other contract reserves	(3,384,000)	(4,815,000)
Foreign and state operating loss carryforwards	(2,344,000)	(2,253,000)
Less: Valuation allowance	2,008,000	1,971,000
Gross deferred tax assets	(53,012,000)	(56,820,000)
Net deferred tax liabilities	$ 174,060,000	$ 141,638,000