CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Income Statement [Abstract]
Revenues	$ 121,762	$ 115,686	$ 370,951	$ 332,108
Costs of services (exclusive of depreciation and amortization)	88,304	83,805	269,462	233,412
Selling, general and administrative expenses	22,194	22,449	67,742	68,929
Depreciation and amortization	3,244	2,527	9,293	7,696
Income from operations	8,020	6,905	24,454	22,071
Interest expense, net	(277)	(424)	(1,011)	(954)
Foreign currency gains (losses), net	(217)	210	1,103	(379)
Income before provision for income taxes	7,526	6,691	24,546	20,738
Provision for income taxes	2,123	952	6,744	4,754
Net income	$ 5,403	$ 5,739	$ 17,802	$ 15,984
Net income per share:
Basic (in dollars per share)	$ 0.69	$ 0.74	$ 2.28	$ 2.02
Diluted (in dollars per share)	$ 0.68	$ 0.71	$ 2.23	$ 1.94
Weighted average number of shares outstanding:
Basic (in shares)	7,771	7,769	7,780	7,903
Diluted (in shares)	7,934	8,050	7,964	8,205