AVAILABLE-FOR-SALE SECURITIES - Amortized Cost and Fair Value of AFS Investments by Collateral Type (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Face Value		$ 1,281,829,317	$ 884,520,701
Unamortized premium		23,818,687	17,748,138
Unamortized discount
Designated credit reserve and OTTI		0	(1,929,833)
Net, unamortized		(2,204,562)	(27,841,262)
Amortized Cost		1,303,443,442	872,497,744
Gross unrealized gain		751,458	3,408,141
Gross unrealized (loss)		(13,369,252)	(10,240,388)
Available-for-sale securities	[1]	1,290,825,648	870,929,601
Credit reserves		0	(541,342)	$ (745,492)
Agency
Schedule of Available-for-sale Securities [Line Items]
Face Value		1,274,329,317	779,219,115
Unamortized premium		23,818,687	17,748,138
Unamortized discount
Designated credit reserve and OTTI		0	0
Net, unamortized		(491,020)	(1,311,292)
Amortized Cost		1,297,656,984	795,655,961
Gross unrealized gain		751,458	2,663,975
Gross unrealized (loss)		(13,324,794)	(8,129,703)
Available-for-sale securities		1,285,083,648	790,190,233
Non-Agency, Excluding Interest-Only
Schedule of Available-for-sale Securities [Line Items]
Face Value		0	4,393,771
Unamortized premium		0	0
Unamortized discount
Designated credit reserve and OTTI		0	(1,929,833)
Net, unamortized		0	(369,887)
Amortized Cost		0	2,094,051
Gross unrealized gain		0	234,647
Gross unrealized (loss)		0	0
Available-for-sale securities		0	2,328,698
Interest-only securities, notional amount			509,109,248
Interest-only securities, book value			14,712,374
Interest-only securities, unrealized loss			9,448,271
Interest-only securities, fair value			5,264,104
Multi-Family
Schedule of Available-for-sale Securities [Line Items]
Face Value		7,500,000	100,907,815
Unamortized premium		0	0
Unamortized discount
Designated credit reserve and OTTI		0	0
Net, unamortized		(1,713,542)	(26,160,083)
Amortized Cost		5,786,458	74,747,732
Gross unrealized gain		0	509,519
Gross unrealized (loss)		(44,458)	(2,110,685)
Available-for-sale securities		5,742,000	73,146,566
Credit Reserve
Unamortized discount
Credit reserves		$ 0	1,929,833
Agency, Non-Agency, Multi-Family, Excluding Interest-Only
Unamortized discount
Available-for-sale securities			$ 865,665,497

[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