UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenue	$ 402,725	$ 365,424	$ 1,169,564	$ 1,043,652
Direct costs	283,461	261,546	832,687	747,889
Gross profit	119,264	103,878	336,877	295,763
Selling, general and administrative expenses	88,972	75,852	251,617	235,614
Depreciation and amortization	1,026	1,308	3,420	4,081
Income from operations	29,266	26,718	81,840	56,068
Other expense, net	1,448	938	5,845	3,746
Income from operations, before income taxes	27,818	25,780	75,995	52,322
Income tax expense	7,650	7,017	21,378	14,568
Net income	20,168	18,763	54,617	37,754
Other comprehensive income (loss), net of tax:
Defined benefit pension plans	0	0	3,103	0
Change in fair value of interest rate swaps	152	118	1,101	(1,473)
Comprehensive income	$ 20,320	$ 18,881	$ 58,821	$ 36,281
Earnings per share – basic (in dollars per share)	$ 0.99	$ 0.90	$ 2.64	$ 1.79
Earnings per share - diluted (in dollars per share)	$ 0.96	$ 0.89	$ 2.57	$ 1.77
Weighted average shares outstanding – basic (in shares)	20,429	20,782	20,676	21,041
Weighted average shares outstanding – diluted (in shares)	21,098	21,180	21,260	21,369