PRO FORMA FINANCIAL INFORMATION - Schedule of Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net income attributable to common stockholders, per:
Weighted-average number of common shares outstanding, basic (in shares)	59,323,799	43,655,292	59,254,895	41,324,795
Weighted-average number of common shares outstanding, diluted (in shares)	59,543,781	44,096,297	59,510,164	41,791,470
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Revenues	$ 63,015	$ 50,307	$ 125,752	$ 100,341
Depreciation and amortization	16,583	12,259	33,191	24,574
Net income attributable to common stockholders	$ 23,889	$ 17,204	$ 45,394	$ 8,655
Net income attributable to common stockholders, per:
Basic common share (in dollars per share)	$ 0.40	$ 0.39	$ 0.77	$ 0.21
Diluted common share (in dollars per share)	$ 0.40	$ 0.39	$ 0.76	$ 0.21
Weighted-average number of common shares outstanding, basic (in shares)	59,323,799	43,655,292	59,254,895	41,324,795
Weighted-average number of common shares outstanding, diluted (in shares)	59,543,781	44,096,297	59,510,164	41,791,470