AVAILABLE-FOR-SALE SECURITIES - Components of Interest Income on AFS Securities (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Coupon interest	$ 3,829,055	$ 6,362,134	$ 12,152,397	$ 11,784,968
Net (premium amortization)/ discount accretion	(159,679)	296,545	(1,403,431)	1,696,333
Interest income	3,669,376	6,658,679	10,748,966	13,481,301
Agency
Schedule of Available-for-sale Securities [Line Items]
Coupon interest	3,829,055	6,362,134	12,152,397	11,742,714
Net (premium amortization)/ discount accretion	(159,679)	(214,920)	(1,435,534)	251,371
Interest income	3,669,376	6,147,214	10,716,863	11,994,085
Non-Agency
Schedule of Available-for-sale Securities [Line Items]
Coupon interest	0	0	0	42,254
Net (premium amortization)/ discount accretion	0	0	0	9,946
Interest income	0	0	0	52,200
Multi-Family
Schedule of Available-for-sale Securities [Line Items]
Coupon interest	0	0	0	0
Net (premium amortization)/ discount accretion	0	511,465	32,103	1,435,016
Interest income	$ 0	$ 511,465	$ 32,103	$ 1,435,016