INVESTMENTS IN REAL ESTATE SECURITIES - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment	$ 1,509	$ 1,765	$ 8,736	$ 7,838
Real estate securities acquired with credit quality deterioration, face amount			2,408,400
Real estate securities acquired with credit quality deterioration, expected cash flows			2,105,100
Real estate securities acquired with credit quality deterioration, fair value			1,370,800
Agency RMBS
Schedule of Available-for-sale Securities [Line Items]
Face amount of securities sold, unsettled	1,700,000		1,700,000
Face amount of securities purchased	1,000,000		1,000,000
Proceeds from sale of AFS, unsettled	1,800,000		1,800,000
Purchase of real estate securities, unsettled	1,100,000		1,100,000
Non-Agency
Schedule of Available-for-sale Securities [Line Items]
Face amount of securities sold, unsettled	30,800		30,800
Purchase of real estate securities, unsettled	$ 12,500		$ 12,500