AVAILABLE-FOR-SALE SECURITIES - Components of Interest Income on AFS Securities (Details) - USD ($)	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]
Coupon interest	$ 7,870,458	$ 4,827,050	$ 19,655,427	$ 11,523,259
Net (premium amortization)/ discount accretion	(43,177)	1,722,819	1,653,155	5,257,442
Interest income	7,827,281	6,549,869	21,308,582	16,780,701
Agency
Schedule of Available-for-sale Securities [Line Items]
Coupon interest	7,870,458	4,006,740	19,613,173	8,629,039
Net (premium amortization)/ discount accretion	(514,600)	118,440	(263,230)	222,570
Interest income	7,355,858	4,125,180	19,349,943	8,851,609
Non-Agency
Schedule of Available-for-sale Securities [Line Items]
Coupon interest	0	581,097	42,254	2,139,698
Net (premium amortization)/ discount accretion	0	359,052	9,946	1,235,030
Interest income	0	940,149	52,200	3,374,728
Multi-Family
Schedule of Available-for-sale Securities [Line Items]
Coupon interest	0	239,213	0	754,522
Net (premium amortization)/ discount accretion	471,423	1,245,327	1,906,439	3,799,842
Interest income	$ 471,423	$ 1,484,540	$ 1,906,439	$ 4,554,364