UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Revenue	$ 437,620	$ 402,725	$ 1,291,103	$ 1,169,564
Direct costs	310,950	283,461	909,475	832,687
Gross profit	126,670	119,264	381,628	336,877
Selling, general and administrative expenses	94,306	88,972	285,502	251,617
Depreciation and amortization	1,045	1,026	3,214	3,420
Income from operations	31,319	29,266	92,912	81,840
Other expense (income), net	906	1,448	(333)	5,845
Income from operations, before income taxes	30,413	27,818	93,245	75,995
Income tax expense	8,151	7,650	24,886	21,378
Net income	22,262	20,168	68,359	54,617
Other comprehensive income, net of tax:
Defined benefit pension plans	0	0	0	3,103
Change in fair value of interest rate swaps		152	(615)	1,101
Comprehensive income	$ 22,262	$ 20,320	$ 67,744	$ 58,821
Earnings per share – basic (in dollars per share)	$ 1.11	$ 0.99	$ 3.38	$ 2.64
Earnings per share - diluted (in dollars per share)	$ 1.09	$ 0.96	$ 3.31	$ 2.57
Weighted average shares outstanding – basic (in shares)	20,022	20,429	20,206	20,676
Weighted average shares outstanding – diluted (in shares)	20,450	21,098	20,634	21,260