EQUITY STRUCTURE AND ACCOUNTS - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
AOCI Attributable to Parent [Roll Forward]
December 31, 2014			$ 15,656
Other comprehensive income (loss)	$ 15,992	$ (18,563)	(4,119)	$ 11,651	$ 18,016
Exchange of noncontrolling interest for common stock			0
September 30, 2015	14,443		14,443		15,656
Accumulated Other Comprehensive Income
AOCI Attributable to Parent [Roll Forward]
December 31, 2014			15,656
Other comprehensive income (loss)			(2,027)		488
Exchange of noncontrolling interest for common stock			620		324
Rebalancing of ownership percentage between Company and Operating Partnership			194
September 30, 2015	14,443		14,443		15,656
Accumulated Other Comprehensive Income of Noncontrolling Interests
AOCI Attributable to Parent [Roll Forward]
December 31, 2014			14,494
Other comprehensive income (loss)			(2,092)
Exchange of noncontrolling interest for common stock			(620)
Rebalancing of ownership percentage between Company and Operating Partnership			(194)
September 30, 2015	11,588		11,588		14,494
Total Accumulated Other Comprehensive Income
AOCI Attributable to Parent [Roll Forward]
December 31, 2014			30,150
Other comprehensive income (loss)			(4,119)
Exchange of noncontrolling interest for common stock			0
Rebalancing of ownership percentage between Company and Operating Partnership			0
September 30, 2015	$ 26,031		$ 26,031		$ 30,150