EQUITY STRUCTURE AND ACCOUNTS - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
AOCI Attributable to Parent [Roll Forward]
December 31, 2014	$ 15,656
Other comprehensive income (loss)	(36,545)	$ 18,016	$ (20,361)
Exchange of noncontrolling interest for common stock	0
September 30, 2015	(3,556)	15,656
Accumulated Other Comprehensive Income
AOCI Attributable to Parent [Roll Forward]
December 31, 2014	15,656
Other comprehensive income (loss)	(20,046)	488
Exchange of noncontrolling interest for common stock	645	324
Rebalancing of ownership percentage between Company and Operating Partnership	189
September 30, 2015	(3,556)	15,656
Accumulated Other Comprehensive Income of Noncontrolling Interests
AOCI Attributable to Parent [Roll Forward]
December 31, 2014	14,494
Other comprehensive income (loss)	(16,499)
Exchange of noncontrolling interest for common stock	(645)
Rebalancing of ownership percentage between Company and Operating Partnership	(189)
September 30, 2015	(2,839)	14,494
Total Accumulated Other Comprehensive Income
AOCI Attributable to Parent [Roll Forward]
December 31, 2014	30,150
Other comprehensive income (loss)	(36,545)
Exchange of noncontrolling interest for common stock	0
Rebalancing of ownership percentage between Company and Operating Partnership	0
September 30, 2015	$ (6,395)	$ 30,150