UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net service revenues	$ 341,053	$ 336,460	$ 1,015,354	$ 993,708
Direct costs of services	236,678	231,080	709,925	684,857
Gross profit	104,375	105,380	305,429	308,851
Selling, general and administrative expenses	81,921	87,803	249,105	258,732
Depreciation and amortization	2,110	2,075	6,213	6,654
Income from operations	20,344	15,502	50,111	43,465
Other expense, net	1,364	778	3,906	2,277
Income before income taxes	18,980	14,724	46,205	41,188
Income tax expense	8,881	5,704	19,060	17,654
Net income	10,099	9,020	27,145	23,534
Other comprehensive (loss) income:
Defined benefit pension plans, net of tax	(278)	(2)	(287)	(7)
Change in fair value of interest rate swap, net of tax	60	0	(52)	0
Comprehensive income	$ 9,881	$ 9,018	$ 26,806	$ 23,527
Earnings per share – basic (in dollars per share)	$ 0.40	$ 0.35	$ 1.07	$ 0.90
Earnings per share – diluted (in dollars per share)	$ 0.40	$ 0.34	$ 1.06	$ 0.89
Weighted average shares outstanding – basic (in shares)	25,296	25,996	25,264	26,287
Weighted average shares outstanding – diluted (in shares)	25,535	26,173	25,565	26,449
Dividends declared per share (in dollars per share)	$ 0.12	$ 0.12	$ 0.36	$ 0.36