CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue	$ 1,579,922	$ 1,397,700	$ 1,347,387
Direct costs	1,123,058	1,001,476	952,349
Gross profit	456,864	396,224	395,038
Selling, general and administrative expenses	345,721	310,713	314,167
Depreciation and amortization	4,500	5,255	6,050
Income from operations	106,643	80,256	74,821
Other expense, net	7,376	5,044	3,425
Income from continuing operations, before income taxes	99,267	75,212	71,396
Income tax expense	24,090	19,173	16,830
Income from continuing operations	75,177	56,039	54,566
Income from discontinued operations, net of tax	0	0	76,296
Net income	75,177	56,039	130,862
Other comprehensive (loss) income:
Defined benefit pension plans, net of tax	3,103	(1,706)	(2,183)
Change in fair value of interest rate swap, net of tax	1,941	(1,191)	(807)
Comprehensive income	$ 80,221	$ 53,142	$ 127,872
Earnings per share - basic:
Continuing operations (in dollars per share)	$ 3.65	$ 2.67	$ 2.35
Discontinued operations (in dollars per share)	0	0	3.29
Earnings per share – basic (in dollars per share)	3.65	2.67	5.64
Earnings per share - diluted:
Continuing operations (in dollars per share)	3.54	2.62	2.29
Discontinued operations (in dollars per share)	0	0	3.21
Earnings per share – diluted (in dollars per share)	$ 3.54	$ 2.62	$ 5.50
Weighted average shares outstanding - basic (in shares)	20,579	20,983	23,186
Weighted average shares outstanding – diluted (in shares)	21,212	21,395	23,772