Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets
Allowance for expected credit losses	$ 1,825	$ 1,687
Accrued paid time off	2,504	2,423
Foreign net operating loss (NOL) carry forward	91	957
State net operating loss (NOL) carry forward	522	714
Stock option compensation	1,680	2,308
Deferred rent	2,566	3,091
Deferred compensation	5,358	4,598
Foreign tax credits	6,677	5,882
Foreign exchange	4,014	5,370
Foreign deferred	727	650
Accrued bonus	5,303	4,126
Accrued liabilities and other	6,660	5,701
Deferred Tax Assets, gross, before valuation allowance	39,008	39,615
Less: Valuation Allowance	(7,048)	(6,839)	$ (5,374)	$ (5,112)
Total Deferred Tax Assets	31,960	32,776
Deferred Tax Liabilities
Retention	(637)	(1,003)
Prepaid expenses	(726)	(1,089)
Payroll taxes	(544)	(489)
Unbilled revenue	(607)	(1,451)
Depreciation	(1,920)	(1,731)
Amortization	(68,194)	(60,392)
Deferred gain and other	(1,245)	(951)
Total Deferred Tax Liabilities	(73,873)	(67,106)
Total Net Deferred Tax Liability	(41,913)	(34,330)
State and Local Jurisdiction
Deferred Tax Assets
Tax credits	$ 1,081	$ 2,108