INVESTMENTS IN REAL ESTATE SECURITIES - Narrative (Details) - USD ($) $ in Thousands					1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2015	May. 30, 2014	Mar. 06, 2014	Jun. 27, 2013	Jan. 31, 2014	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Purchase of Non-Agency RMBS														$ 1,252,516		$ 1,690,770	$ 407,689
Proceeds from sale of Non-Agency RMBS														425,761		1,288,980	521,865
Other-than-temporary impairment (OTTI) on securities					$ 1,000	$ 2,494	$ 1,574	$ 649	$ 1,071	$ 448	$ 0	$ 615	$ 328	5,788		1,391	4,993
Other-than-temporary (OTTI) credit loss related to securities in an unrealized loss position																	300
Real estate securities acquired during the period with credit quality deterioration, face amount														583,600		754,600
Real estate securities acquired during the period with credit quality deterioration, expected cash flows	$ 502,300					502,300				734,900				502,300		734,900
Real estate securities acquired during the period with credit quality deterioration, fair value	329,500					$ 329,500				$ 552,100				329,500		552,100
Assets Held Prior to Spin-Off [Member]
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment (OTTI) on securities																	$ 3,800
Non-Agency RMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Face amount of securities sold														476,400	[1]	2,004,300
Face amount of securities purchased			$ 625,000											2,397,900	[1]	3,187,500
Sale price of securities sold														425,700	[1]	1,289,000
Purchases/additional fundings														1,288,900	[1]	1,455,800
Purchase of Non-Agency RMBS			$ 553,000
Percentage of mezzanine and subordinate tranche purchased			75.00%
Proceeds from sale of Non-Agency RMBS		$ 598,500
Gain on sale of debt investments		$ 39,700												3,000	[1]	60,600
Agency RMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Face amount of securities sold	1,500,000													5,772,500		746,900
Face amount of securities purchased	700,000			$ 22,700										5,140,100		1,341,000
Sale price of securities sold	1,500,000													6,007,600		796,400
Purchases/additional fundings	$ 700,000													5,333,700		1,399,000
Gain on sale of debt investments														$ 10,100		$ 5,100

[1] Purchases include $431.0 million face of servicer advance bonds for a purchase price of $431.0 million.