Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 4,353,026	$ (4,256,337)	$ (5,822,037)	$ (4,183,767)
Other comprehensive income (loss):
Increase (decrease) in unrealized gain (loss) on available-for-sale securities, net	0	(4,175,111)	0	(2,954,193)
Reclassification adjustment for net gain (loss) included in net income (loss)	0	6,362,159	12,617,794	6,579,724
Total other comprehensive income (loss)	0	2,187,048	12,617,794	3,625,531
Less: Dividends to preferred stockholders	(880,509)	(880,509)	(2,631,744)	(2,631,744)
Comprehensive income (loss) attributable to common stockholders	$ 3,472,517	$ (2,949,798)	$ 4,164,013	$ (3,189,980)