PRO FORMA FINANCIAL INFORMATION - Schedule of Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net income attributable to common stockholders, per:
Weighted-average number of common shares outstanding, basic (in shares)	65,160,290	47,359,949	61,244,991	43,358,620
Weighted-average number of common shares outstanding, diluted (in shares)	65,398,175	47,877,202	61,468,603	43,840,550
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Revenues	$ 61,278	$ 62,411	$ 190,186	$ 186,682
Depreciation and amortization	16,946	16,353	50,997	49,214
Net income attributable to common stockholders	$ 20,548	$ 27,785	$ 64,399	$ 56,086
Net income attributable to common stockholders, per:
Basic common share (in dollars per share)	$ 0.32	$ 0.59	$ 1.05	$ 1.29
Diluted common share (in dollars per share)	$ 0.31	$ 0.58	$ 1.05	$ 1.28
Weighted-average number of common shares outstanding, basic (in shares)	65,160,290	47,359,949	61,244,991	43,358,620
Weighted-average number of common shares outstanding, diluted (in shares)	65,398,175	47,877,202	61,468,603	43,840,550