ACQUISITIONS (Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Business Combinations [Abstract]
Revenue, as reported	$ 295,630	$ 220,252
Revenue, proforma	295,600	270,300
Net income, as reported	21,174	15,730
Net income, proforma	$ 21,200	$ 16,600
Basic earnings per share, as reported	$ 0.45	$ 0.33
Basic earnings per share, proforma	0.45	0.35
Diluted earnings per share, as reported	0.45	0.33
Diluted earnings per share, proforma	$ 0.45	$ 0.35
Revenue of acquiree since acquisition date	$ 56,200
Earnings of acquiree since acquisition date	$ 900