SEGMENT REPORTING (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
SEGMENT REPORTING
Number of reportable segments | segment			3
Interest income	$ 63,013,000	$ 48,459,000	$ 178,635,000	$ 130,394,000
Interest expense	(29,535,000)	(19,928,000)	(83,846,000)	(51,521,000)
Net interest income	33,478,000	28,531,000	94,789,000	78,873,000
Provision for loan losses	(150,000)	(150,000)	(450,000)	(450,000)
Net interest income after provision for loan losses	33,328,000	28,381,000	94,339,000	78,423,000
Operating lease income	20,671,000	12,810,000	60,207,000	38,827,000
Tenant recoveries	2,847,000	2,252,000	7,883,000	6,473,000
Sale of loans, net	15,165,000	20,414,000	59,717,000	107,135,000
Realized gain on securities	513,000	14,074,000	23,680,000	21,259,000
Unrealized gain (loss) on Agency interest-only securities	731,000	(1,282,000)	(639,000)	466,000
Realized gain on sale of real estate, net	6,406,000	8,471,000	21,347,000	24,225,000
Fee income	3,483,000	2,715,000	10,857,000	7,216,000
Net result from derivative transactions	(42,242,000)	1,125,000	(54,594,000)	(50,435,000)
Earnings (loss) from investment in unconsolidated joint ventures	(25,000)	326,000	580,000	1,662,000
Gain on assignment of mortgage loan financing	0	432,000	0	432,000
Total other income	7,549,000	61,337,000	129,038,000	157,260,000
Salaries and employee benefits	(17,628,000)	(19,830,000)	(47,333,000)	(66,316,000)
Operating expenses	(4,951,000)	(6,190,000)	(20,487,000)	(12,896,000)
Real estate operating expenses	(8,975,000)	(7,150,000)	(27,976,000)	(22,131,000)
Real estate acquisition costs	(470,000)	(1,712,000)	(1,524,000)	(1,712,000)
Fee expense	(675,000)	(496,000)	(3,260,000)	(1,711,000)
Depreciation and amortization	(9,561,000)	(6,829,000)	(29,238,000)	(21,274,000)
Total costs and expenses	(42,260,000)	(42,207,000)	(129,818,000)	(126,040,000)
Tax (expense) benefit	4,181,000	(10,335,000)	(4,101,000)	(23,823,000)
Net income	2,798,000	37,176,000	89,458,000	85,820,000
Total assets	5,829,961,000		5,829,961,000		$ 5,814,235,000
Company’s investment in unconsolidated joint ventures	33,793,000		33,793,000		6,041,000
Investment in FHLB stock	77,915,000		77,915,000		72,340,000
Deferred tax assets	11,400,000		11,400,000		8,200,000
Senior unsecured notes	611,981,000		611,981,000		610,129,000
Operating Segment | Loans
SEGMENT REPORTING
Interest income	45,195,000	30,348,000	120,932,000	78,389,000
Interest expense	(6,749,000)	(2,748,000)	(17,509,000)	(8,532,000)
Net interest income	38,446,000	27,600,000	103,423,000	69,857,000
Provision for loan losses	(150,000)	(150,000)	(450,000)	(450,000)
Net interest income after provision for loan losses	38,296,000	27,450,000	102,973,000	69,407,000
Operating lease income	0	0	0	0
Tenant recoveries	0	0	0	0
Sale of loans, net	15,165,000	20,414,000	59,717,000	107,135,000
Realized gain on securities	0	0	0	0
Unrealized gain (loss) on Agency interest-only securities	0	0	0	0
Realized gain on sale of real estate, net	519,000	339,000	1,771,000	1,122,000
Fee income	905,000	999,000	3,990,000	2,352,000
Net result from derivative transactions	(13,159,000)	2,137,000	(18,335,000)	(17,731,000)
Earnings (loss) from investment in unconsolidated joint ventures	0	0	0	0
Gain on assignment of mortgage loan financing		0		0
Total other income	3,430,000	23,889,000	47,143,000	92,878,000
Salaries and employee benefits	(4,525,000)	(4,300,000)	(11,436,000)	(18,800,000)
Operating expenses	132,000	(89,000)	301,000	0
Real estate operating expenses	0	0	0	0
Real estate acquisition costs	0	0	0	0
Fee expense	156,000	(312,000)	(1,642,000)	(1,034,000)
Depreciation and amortization	0	0	0	0
Total costs and expenses	(4,237,000)	(4,701,000)	(12,777,000)	(19,834,000)
Tax (expense) benefit	0	0	0	0
Net income	37,489,000	46,638,000	137,339,000	142,451,000
Total assets	2,128,343,000		2,128,343,000		1,939,008,000
Operating Segment | Securities
SEGMENT REPORTING
Interest income	17,811,000	18,190,000	57,659,000	52,058,000
Interest expense	(1,753,000)	(1,546,000)	(5,512,000)	(4,349,000)
Net interest income	16,058,000	16,644,000	52,147,000	47,709,000
Provision for loan losses	0	0	0	0
Net interest income after provision for loan losses	16,058,000	16,644,000	52,147,000	47,709,000
Operating lease income	0	0	0	0
Tenant recoveries	0	0	0	0
Sale of loans, net	0	0	0	0
Realized gain on securities	513,000	14,074,000	23,680,000	21,259,000
Unrealized gain (loss) on Agency interest-only securities	731,000	(1,282,000)	(639,000)	466,000
Realized gain on sale of real estate, net	0	0	0	0
Fee income	230,000	(96,000)	230,000	0
Net result from derivative transactions	(29,083,000)	(1,012,000)	(36,259,000)	(32,704,000)
Earnings (loss) from investment in unconsolidated joint ventures	0	0	0	0
Gain on assignment of mortgage loan financing		0		0
Total other income	(27,609,000)	11,684,000	(12,988,000)	(10,979,000)
Salaries and employee benefits	0	0	0	0
Operating expenses	0	0	0	0
Real estate operating expenses	0	0	0	0
Real estate acquisition costs	0	0	0	0
Fee expense	(10,000)	(14,000)	(31,000)	(53,000)
Depreciation and amortization	0	0	0	0
Total costs and expenses	(10,000)	(14,000)	(31,000)	(53,000)
Tax (expense) benefit	0	0	0	0
Net income	(11,561,000)	28,314,000	39,128,000	36,677,000
Total assets	2,415,382,000		2,415,382,000		2,815,566,000
Operating Segment | Real Estate
SEGMENT REPORTING
Interest income	0	0	0	0
Interest expense	(6,365,000)	(4,663,000)	(17,670,000)	(11,777,000)
Net interest income	(6,365,000)	(4,663,000)	(17,670,000)	(11,777,000)
Provision for loan losses	0	0	0	0
Net interest income after provision for loan losses	(6,365,000)	(4,663,000)	(17,670,000)	(11,777,000)
Operating lease income	20,671,000	12,810,000	60,207,000	38,827,000
Tenant recoveries	2,847,000	2,252,000	7,883,000	6,473,000
Sale of loans, net	0	0	0	0
Realized gain on securities	0	0	0	0
Unrealized gain (loss) on Agency interest-only securities	0	0	0	0
Realized gain on sale of real estate, net	5,887,000	8,132,000	19,576,000	23,103,000
Fee income	6,000	92,000	33,000	92,000
Net result from derivative transactions	0	0	0	0
Earnings (loss) from investment in unconsolidated joint ventures	(25,000)	225,000	464,000	675,000
Gain on assignment of mortgage loan financing		432,000		432,000
Total other income	29,386,000	23,943,000	88,163,000	69,602,000
Salaries and employee benefits	0	0	0	0
Operating expenses	(17,000)	0	(16,000)	0
Real estate operating expenses	(8,975,000)	(7,150,000)	(27,976,000)	(22,131,000)
Real estate acquisition costs	(470,000)	(1,712,000)	(1,524,000)	(1,712,000)
Fee expense	(123,000)	(46,000)	(230,000)	(87,000)
Depreciation and amortization	(9,533,000)	(6,692,000)	(29,158,000)	(20,863,000)
Total costs and expenses	(19,118,000)	(15,600,000)	(58,904,000)	(44,793,000)
Tax (expense) benefit	0	0	0	0
Net income	3,903,000	3,680,000	11,589,000	13,032,000
Total assets	871,591,000		871,591,000		771,129,000
Corporate / Other
SEGMENT REPORTING
Interest income	7,000	(79,000)	44,000	(53,000)
Interest expense	(14,668,000)	(10,971,000)	(43,155,000)	(26,863,000)
Net interest income	(14,661,000)	(11,050,000)	(43,111,000)	(26,916,000)
Provision for loan losses	0	0	0	0
Net interest income after provision for loan losses	(14,661,000)	(11,050,000)	(43,111,000)	(26,916,000)
Operating lease income	0	0	0	0
Tenant recoveries	0	0	0	0
Sale of loans, net	0	0	0	0
Realized gain on securities	0	0	0	0
Unrealized gain (loss) on Agency interest-only securities	0	0	0	0
Realized gain on sale of real estate, net	0	0	0	0
Fee income	2,342,000	1,720,000	6,604,000	4,772,000
Net result from derivative transactions	0	0	0	0
Earnings (loss) from investment in unconsolidated joint ventures	0	101,000	116,000	987,000
Gain on assignment of mortgage loan financing		0		0
Total other income	2,342,000	1,821,000	6,720,000	5,759,000
Salaries and employee benefits	(13,103,000)	(15,530,000)	(35,897,000)	(47,516,000)
Operating expenses	(5,066,000)	(6,101,000)	(20,772,000)	(12,896,000)
Real estate operating expenses	0	0	0	0
Real estate acquisition costs	0	0	0	0
Fee expense	(698,000)	(124,000)	(1,357,000)	(537,000)
Depreciation and amortization	(28,000)	(137,000)	(80,000)	(411,000)
Total costs and expenses	(18,895,000)	(21,892,000)	(58,106,000)	(61,360,000)
Tax (expense) benefit	4,181,000	(10,335,000)	(4,101,000)	(23,823,000)
Net income	(27,033,000)	(41,456,000)	(98,598,000)	(106,340,000)
Total assets	414,645,000		414,645,000		288,532,000
Grace Lake JV, LLC
SEGMENT REPORTING
Earnings (loss) from investment in unconsolidated joint ventures	196,000	225,000	685,000	675,000
Company’s investment in unconsolidated joint ventures	2,753,000		2,753,000		2,143,000
LCRIP I
SEGMENT REPORTING
Fee income	0	83,873	77,447	312,417
Earnings (loss) from investment in unconsolidated joint ventures	0	$ 101,000	116,000	$ 987,000
Company’s investment in unconsolidated joint ventures	$ 49,000		$ 49,000		$ 3,898,000