INVESTMENTS IN REAL ESTATE SECURITIES - Narrative (Details) (USD $)	1 Months Ended	3 Months Ended								12 Months Ended			0 Months Ended					1 Months Ended	0 Months Ended
	Jan. 31, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 26, 2014 Investment	Aug. 25, 2014 Investment	May 30, 2014	May 27, 2014 Investment	Mar. 06, 2014	Dec. 31, 2014	Jun. 27, 2013
Schedule of Available-for-sale Securities [Line Items]
Purchase of Non-Agency RMBS										$ 1,745,165,000	$ 407,689,000	$ 0
Proceeds from sale of Non-Agency RMBS										1,288,980,000	521,865,000	0
Face amount of mortgage loans						57,552,000					57,552,000
Other-than-temporary impairment (OTTI) losses										1,400,000
Other-than-temporary impairment (OTTI) on securities	1,000,000	448,000	0	615,000	328,000	1,237,000	0	3,756,000	0	1,391,000	4,993,000	0
Other-than-temporary (OTTI) credit loss related to securities in an unrealized loss position	300,000
Real estate securities acquired during the period with credit quality deterioration, face amount		800,000,000				1,100,000,000				800,000,000	1,100,000,000							800,000,000
Real estate securities acquired during the period with credit quality deterioration, expected cash flows		734,900,000				900,000,000				734,900,000	900,000,000							734,900,000
Real estate securities acquired during the period with credit quality deterioration, fair value		552,100,000				700,000,000				552,100,000	700,000,000							552,100,000
Non-Agency RMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Face amount of securities purchased										3,200,000,000	1,300,000,000						625,000,000	186,700,000
Purchase of Non-Agency RMBS										1,500,000,000							553,000,000
Face amount of securities sold		2,000,000,000				729,700,000				2,000,000,000	729,700,000		27,900,000	15,400,000				2,000,000,000
Proceeds from sale of real estate securities										1,300,000,000	521,900,000
Amortized cost basis of securities sold										1,200,000,000			24,000,000	13,100,000	558,800,000
Gain (loss) on sale of debt investments										60,600,000	52,700,000				39,700,000
Payments to acquire securities										114,300,000	835,600,000
Percentage of mezzanine and subordinate tranche purchased																	75.00%
Mortgage loans pledged																	900,000,000
Proceeds from sale of Non-Agency RMBS															598,500,000
Loan count													25	19		16
Face amount of mortgage loans																17,400,000
Amortized cost basis of mortgage loans																12,000,000
Non-Agency RMBS Excluding Other ABS [Member]
Schedule of Available-for-sale Securities [Line Items]
Face amount of securities paid down							2,600,000
Carrying value of securities paid down							2,100,000
Interest income of securities paid down							600,000
Loan count							4
Agency RMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Face amount of securities purchased										1,300,000,000	608,900,000								22,700,000
Purchase of Non-Agency RMBS										1,400,000,000
Floating rate securities		300,000,000								300,000,000								300,000,000
Fixed rate specified pools		1,000,000,000								1,000,000,000								1,000,000,000
Face amount of securities sold		746,900,000								746,900,000								746,900,000
Proceeds from sale of real estate securities										796,400,000
Amortized cost basis of securities sold										791,700,000
Gain (loss) on sale of debt investments										4,700,000
Payments to acquire securities							1,200,000				645,500,000								1,200,000
Agency RMBS contributed from Newcastle, face amount											1,000,000,000
Assets Held Prior to Spin-Off [Member]
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment (OTTI) on securities											3,800,000
Repurchase Agreements [Member] | Non-Agency RMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Repurchase agreements		$ 84,600,000								$ 84,600,000								$ 84,600,000