SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($)			3 Months Ended	12 Months Ended			13 Months Ended
		Mar. 08, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Sep. 30, 2016	Dec. 15, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale securities	[1]			$ 1,290,825,648	$ 870,929,601		$ 870,929,601
Backstop deferred income amortization period				5 years
Backstop guarantee, assumed prepayment rate				15.00%
Common stock, shares authorized (in shares)				450,000,000	450,000,000		450,000,000
Common stock, par value (in dollars per share)				$ 0.01	$ 0.01		$ 0.01
Common stock, shares issued (in shares)				22,143,758	17,539,258		17,539,258
Common stock, shares outstanding (in shares)				22,143,758	17,539,258	14,656,394	17,539,258
Stock repurchase program, authorized amount				$ 10,000,000
Preferred stock, shares authorized (in shares)				50,000,000	50,000,000		50,000,000
Preferred stock, par value (in dollars per share)				$ 0.01	$ 0.01		$ 0.01
Preferred stock, shares issued (in shares)				1,610,000	1,610,000		1,610,000
Preferred stock, shares outstanding (in shares)				1,610,000	1,610,000		1,610,000
Income taxes, interest paid				$ 14,477,370	$ 6,355,591	$ 8,554,565
Non-Agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Maximum exposure to loss from consolidated trusts				27,108,818	24,716,861
Available-for-sale securities				0	7,592,802		$ 7,592,802
Maximum loss exposure from VIEs				0	4,413,403		4,413,403
Multi-Family MBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale securities				5,742,000	73,146,566		73,146,566
Residential mortgage loans
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unpaid mortgage balance				$ 518,455,163
Internal Revenue Service (IRS)
Schedule of Trading Securities and Other Trading Assets [Line Items]
Income taxes, interest paid		$ 2,010,000	$ 2,010,000
Income taxes, interest provision					$ 1,860,000		$ 1,860,000	$ 1,860,000
Income taxes, interest expense		$ 150,000	$ 150,000
Stock Repurchase Program
Schedule of Trading Securities and Other Trading Assets [Line Items]
Stock repurchase program, authorized amount									$ 10,000,000
Common stock shares repurchased (in shares)				0	126,856		126,856
Weighted average share price of common stock repurchased (in dollars per share)					$ 5.09		$ 5.09
Common stock shares repurchased (in shares)				$ 9,400,000

[1] Our consolidated balance sheets include assets and liabilities of consolidated variable interest entities (“VIE's) as the Company is the primary beneficiary of these VIEs. As of December 31, 2017 and December 31, 2016, assets of consolidated VIEs totaled $1,255,404,335 and $1,369,120,941, respectively, and the liabilities of consolidated VIEs totaled $1,228,295,517 and $1,344,404,080, respectively