EQUITY STRUCTURE AND ACCOUNTS - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
AOCI Attributable to Parent [Roll Forward]
December 31, 2015	$ (3,556)
Other comprehensive income (loss)	34,383	$ 18,502	$ (36,545)
Exchange of noncontrolling interest for common stock	(772)		0
March 31, 2016	16,139		(3,556)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent [Roll Forward]
December 31, 2015	(3,556)
Other comprehensive income (loss)	19,467		(20,046)
Exchange of noncontrolling interest for common stock	(122)		645
Rebalancing of ownership percentage between Company and Operating Partnership	350
March 31, 2016	16,139		(3,556)
Accumulated Other Comprehensive Income of Noncontrolling Interests
AOCI Attributable to Parent [Roll Forward]
December 31, 2015	(2,839)
Other comprehensive income (loss)	14,916
Exchange of noncontrolling interest for common stock	122
Rebalancing of ownership percentage between Company and Operating Partnership	(350)
March 31, 2016	11,849		(2,839)
Total Accumulated Other Comprehensive Income
AOCI Attributable to Parent [Roll Forward]
December 31, 2015	(6,395)
Other comprehensive income (loss)	34,383
Exchange of noncontrolling interest for common stock	0
Rebalancing of ownership percentage between Company and Operating Partnership	0
March 31, 2016	$ 27,988		$ (6,395)