ACQUISITIONS (Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Combinations [Abstract]
Revenue, as reported	$ 341,866	$ 311,113	$ 981,466	$ 836,714
Revenue, proforma	341,900	311,100	981,500	896,600
Net income, as reported	30,006	24,470	81,677	70,109
Net income, proforma	$ 30,000	$ 24,500	$ 81,700	$ 71,300
Basic earnings per share, as reported	$ 0.64	$ 0.52	$ 1.74	$ 1.50
Basic earnings per share, proforma	0.64	0.52	1.74	1.52
Diluted earnings per share, as reported	0.63	0.52	1.72	1.48
Diluted earnings per share, proforma	$ 0.63	$ 0.52	$ 1.72	$ 1.51