PRO FORMA FINANCIAL INFORMATION - Schedule of Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net income attributable to common stockholders, per:
Weighted-average number of common shares outstanding, basic (in shares)	65,312,288	65,160,290	65,285,591	61,244,991
Weighted-average number of common shares outstanding, diluted (in shares)	65,591,428	65,398,175	65,470,589	61,468,603
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Revenues	$ 62,858	$ 63,890	$ 204,889	$ 198,021
Depreciation and amortization	17,404	17,714	53,111	53,301
Net income attributable to common stockholders	$ 24,512	$ 22,392	$ 44,842	$ 69,930
Net income attributable to common stockholders, per:
Basic common share (in dollars per share)	$ 0.38	$ 0.34	$ 0.69	$ 1.14
Diluted common share (in dollars per share)	$ 0.37	$ 0.34	$ 0.68	$ 1.14
Weighted-average number of common shares outstanding, basic (in shares)	65,312,288	65,160,290	65,285,591	61,244,991
Weighted-average number of common shares outstanding, diluted (in shares)	65,591,428	65,398,175	65,470,589	61,468,603