ACQUISITIONS (Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Business Combinations [Abstract]
Revenue, as reported	$ 343,970	$ 305,349	$ 639,600	$ 525,601
Revenue, proforma	344,000	315,200	639,600	585,500
Net income, as reported	30,497	29,909	51,671	45,639
Net income, proforma	$ 30,500	$ 30,300	$ 51,700	$ 46,900
Basic earnings per share, as reported	$ 0.65	$ 0.64	$ 1.10	$ 0.97
Basic earnings per share, proforma	0.65	0.65	1.10	1.00
Diluted earnings per share, as reported	0.64	0.64	1.09	0.97
Diluted earnings per share, proforma	$ 0.64	$ 0.64	$ 1.09	$ 0.99