Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 11,315,000	$ 2,369,141
Other comprehensive income (loss):
Increase (decrease) in net unrealized gain (loss) on available-for-sale securities, net	(12,154,936)	3,699,186
Reclassification adjustment for net gain (loss) included in net income (loss)	1,289,589	(148,284)
Total other comprehensive income (loss)	(10,865,347)	3,550,902
Less: Dividends to preferred stockholders	(880,509)	(880,509)
Comprehensive income attributable to common stockholders	$ (430,856)	$ 5,039,534