SEGMENT REPORTING (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
SEGMENT REPORTING
Number of reportable segments | segment									3
Income Statement [Abstract]
Interest income	$ 60,721,000	$ 60,284,000	$ 55,766,000	$ 59,601,000	$ 62,903,000	$ 63,013,000	$ 59,239,000	$ 56,384,000	$ 236,372,000	$ 241,539,000	$ 187,325,000
Interest expense									(120,827,000)	(113,303,000)	(77,574,000)
Net interest income									115,545,000	128,236,000	109,751,000
Provision for loan losses									(300,000)	(600,000)	(600,000)
Net interest income after provision for loan losses	28,517,000	29,599,000	27,214,000	29,915,000	33,297,000	33,328,000	31,602,000	29,409,000	115,245,000	127,636,000	109,151,000
Operating lease income									77,277,000	80,465,000	56,649,000
Tenant recoveries									5,958,000	9,907,000	9,183,000
Sale of loans, net									26,009,000	71,066,000	145,275,000
Realized gain on securities									7,724,000	24,007,000	26,977,000
Unrealized gain (loss) on Agency interest-only securities									(56,000)	(1,249,000)	2,144,000
Realized gain on sale of real estate, net									20,636,000	40,386,000	29,760,000
Fee and other income									21,365,000	15,205,000	11,704,000
Net result from derivative transactions									(1,409,000)	(38,937,000)	(94,798,000)
Earnings (loss) from investment in unconsolidated joint ventures									426,000	371,000	1,990,000
Gain on assignment of mortgage loan financing									0	0	432,000
Gain (loss) on extinguishment of debt									5,382,000	0	(150,000)
Other income (loss)	89,212,000	69,335,000	11,835,000	(7,070,000)	72,183,000	7,549,000	86,452,000	35,037,000			189,166,000
Total other income									163,312,000	201,221,000	189,166,000
Salaries and employee benefits									(64,270,000)	(61,612,000)	(82,144,000)
Operating expenses									(20,552,000)	(25,103,000)	(25,398,000)
Real estate operating expenses									(29,953,000)	(35,886,000)	(32,670,000)
Real estate acquisition costs									(592,000)	(1,983,000)	(2,404,000)
Fee expense									(3,703,000)	(4,521,000)	(3,023,000)
Depreciation and amortization									(39,447,000)	(39,061,000)	(28,447,000)
Total costs and expenses	(45,335,000)	(40,615,000)	(37,405,000)	(35,162,000)	(38,347,000)	(42,260,000)	(44,180,000)	(43,379,000)	(158,517,000)	(168,166,000)	(174,086,000)
Tax (expense) benefit	(773,000)	(8,721,000)	2,301,000	873,000	(10,457,000)	4,181,000	(5,177,000)	(3,104,000)	(6,320,000)	(14,557,000)	(26,605,000)
Net income (loss)	71,621,000	$ 49,598,000	$ 3,945,000	$ (11,444,000)	56,676,000	$ 2,798,000	$ 68,697,000	$ 17,963,000	113,720,000	146,134,000	97,626,000
Total assets	5,578,337,000				5,895,212,000				5,578,337,000	5,895,212,000	5,814,235,000
Investment in unconsolidated joint ventures	34,025,000				33,797,000				34,025,000	33,797,000
Investment in FHLB stock	77,915,000				77,915,000				77,915,000	77,915,000
Operating Segment
Income Statement [Abstract]
Investment in unconsolidated joint ventures	34,000,000.0				33,700,000				34,000,000.0	33,700,000
Operating Segment | Loans
Income Statement [Abstract]
Interest income									161,315,000	165,403,000	113,943,000
Interest expense									(25,531,000)	(24,039,000)	(13,205,000)
Net interest income									135,784,000	141,364,000	100,738,000
Provision for loan losses									(300,000)	(600,000)	(600,000)
Net interest income after provision for loan losses									135,484,000	140,764,000	100,138,000
Operating lease income									0	0	0
Tenant recoveries									0	0	0
Sale of loans, net									26,009,000	71,066,000	145,275,000
Realized gain on securities									0	0	0
Unrealized gain (loss) on Agency interest-only securities									0	0	0
Realized gain on sale of real estate, net									0	2,346,000	1,525,000
Fee and other income									7,547,000	5,999,000	3,854,000
Net result from derivative transactions									8,371,000	(12,609,000)	(34,599,000)
Earnings (loss) from investment in unconsolidated joint ventures									0	0	0
Gain on assignment of mortgage loan financing											0
Gain (loss) on extinguishment of debt									0		0
Other income (loss)											116,055,000
Total other income									41,927,000	66,802,000
Salaries and employee benefits									(11,000,000)	(16,531,000)	(22,400,000)
Operating expenses									0	381,000	235,000
Real estate operating expenses									0	0	0
Real estate acquisition costs									0	0	0
Fee expense									(2,343,000)	(1,693,000)	(2,172,000)
Depreciation and amortization									0	0	0
Total costs and expenses									(13,343,000)	(17,843,000)	(24,337,000)
Tax (expense) benefit									0	0	0
Net income (loss)									164,068,000	189,723,000	191,856,000
Total assets	2,353,977,000				2,310,409,000				2,353,977,000	2,310,409,000	1,939,008,000
Operating Segment | Securities
Income Statement [Abstract]
Interest income									74,987,000	76,083,000	73,331,000
Interest expense									(9,740,000)	(7,256,000)	(6,588,000)
Net interest income									65,247,000	68,827,000	66,743,000
Provision for loan losses									0	0	0
Net interest income after provision for loan losses									65,247,000	68,827,000	66,743,000
Operating lease income									0	0	0
Tenant recoveries									0	0	0
Sale of loans, net									0	0	0
Realized gain on securities									7,724,000	24,007,000	26,977,000
Unrealized gain (loss) on Agency interest-only securities									(56,000)	(1,249,000)	2,144,000
Realized gain on sale of real estate, net									0	0	0
Fee and other income									0	230,000	0
Net result from derivative transactions									(9,780,000)	(26,328,000)	(60,199,000)
Earnings (loss) from investment in unconsolidated joint ventures									0	0	0
Gain on assignment of mortgage loan financing											0
Gain (loss) on extinguishment of debt									0		0
Other income (loss)											(31,078,000)
Total other income									(2,112,000)	(3,340,000)
Salaries and employee benefits									0	0	0
Operating expenses									0	0	0
Real estate operating expenses									0	0	0
Real estate acquisition costs									0	0	0
Fee expense									(166,000)	(40,000)	(65,000)
Depreciation and amortization									0	0	0
Total costs and expenses									(166,000)	(40,000)	(65,000)
Tax (expense) benefit									0	0	0
Net income (loss)									62,969,000	65,447,000	35,600,000
Total assets	2,100,947,000				2,407,217,000				2,100,947,000	2,407,217,000	2,815,566,000
Operating Segment | Real Estate
Income Statement [Abstract]
Interest income									10,000	0	0
Interest expense									(25,333,000)	(23,873,000)	(15,984,000)
Net interest income									(25,323,000)	(23,873,000)	(15,984,000)
Provision for loan losses									0	0	0
Net interest income after provision for loan losses									(25,323,000)	(23,873,000)	(15,984,000)
Operating lease income									77,277,000	80,465,000	56,649,000
Tenant recoveries									5,958,000	9,907,000	9,183,000
Sale of loans, net									0	0	0
Realized gain on securities									0	0	0
Unrealized gain (loss) on Agency interest-only securities									0	0	0
Realized gain on sale of real estate, net									20,636,000	38,040,000	28,235,000
Fee and other income									7,253,000	5,989,000	5,374,000
Net result from derivative transactions									0	0	0
Earnings (loss) from investment in unconsolidated joint ventures									(466,000)	255,000	900,000
Gain on assignment of mortgage loan financing											432,000
Gain (loss) on extinguishment of debt									0		0
Other income (loss)											100,773,000
Total other income									110,658,000	134,656,000
Salaries and employee benefits									0	0	0
Operating expenses									0	0	0
Real estate operating expenses									(29,953,000)	(35,886,000)	(32,670,000)
Real estate acquisition costs									(592,000)	(1,982,000)	(2,400,000)
Fee expense									(618,000)	(470,000)	(83,000)
Depreciation and amortization									(39,354,000)	(38,953,000)	(28,271,000)
Total costs and expenses									(70,517,000)	(77,291,000)	(63,424,000)
Tax (expense) benefit									0	0	0
Net income (loss)									14,818,000	33,492,000	21,365,000
Total assets	856,363,000				868,528,000				856,363,000	868,528,000	771,129,000
Corporate/Other
Income Statement [Abstract]
Interest income									60,000	53,000	51,000
Interest expense									(60,223,000)	(58,135,000)	(41,797,000)
Net interest income									(60,163,000)	(58,082,000)	(41,746,000)
Provision for loan losses									0	0	0
Net interest income after provision for loan losses									(60,163,000)	(58,082,000)	(41,746,000)
Operating lease income									0	0	0
Tenant recoveries									0	0	0
Sale of loans, net									0	0	0
Realized gain on securities									0	0	0
Unrealized gain (loss) on Agency interest-only securities									0	0	0
Realized gain on sale of real estate, net									0	0	0
Fee and other income									6,565,000	2,987,000	2,476,000
Net result from derivative transactions									0	0	0
Earnings (loss) from investment in unconsolidated joint ventures									892,000	116,000	1,090,000
Gain on assignment of mortgage loan financing											0
Gain (loss) on extinguishment of debt									5,382,000		(150,000)
Other income (loss)											3,416,000
Total other income									12,839,000	3,103,000
Salaries and employee benefits									(53,270,000)	(45,081,000)	(59,744,000)
Operating expenses									(20,552,000)	(25,484,000)	(25,633,000)
Real estate operating expenses									0	0	0
Real estate acquisition costs									0	(1,000)	(4,000)
Fee expense									(576,000)	(2,318,000)	(703,000)
Depreciation and amortization									(93,000)	(108,000)	(176,000)
Total costs and expenses									(74,491,000)	(72,992,000)	(86,260,000)
Tax (expense) benefit									(6,320,000)	(14,557,000)	(26,605,000)
Net income (loss)									(128,135,000)	(142,528,000)	(151,195,000)
Total assets	267,050,000				309,058,000				267,050,000	309,058,000	$ 288,532,000
Investment in unconsolidated joint ventures					48,771					48,771
Investment in FHLB stock	77,900,000				77,900,000				77,900,000	77,900,000
Deferred tax assets	2,100,000				5,000,000.0				2,100,000	5,000,000.0
Corporate/Other | Senior Unsecured Notes
Income Statement [Abstract]
Senior Notes	$ 559,800,000				$ 612,600,000				$ 559,800,000	$ 612,600,000