ACQUISITIONS (Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Business Combinations [Abstract]
Revenue, as reported	$ 311,113	$ 239,755	$ 836,714	$ 710,266
Revenue, proforma	311,100	294,800	896,600	865,800
Net income, as reported	24,470	23,664	70,109	61,103
Net income, proforma	$ 24,500	$ 26,400	$ 71,300	$ 67,000
Basic earnings per share, as reported	$ 0.52	$ 0.51	$ 1.50	$ 1.29
Basic earnings per share, proforma	0.52	0.56	1.52	1.42
Diluted earnings per share, as reported	0.52	0.50	1.48	1.28
Diluted earnings per share, proforma	$ 0.52	$ 0.56	$ 1.51	$ 1.40
Revenue of acquiree since acquisition date	$ 127,200
Earnings of acquiree since acquisition date	$ 2,800