Equity - Changes in Stockholders' Equity (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Stockholders' Equity	$ 103,454,467	$ 102,914,687	$ (341,317,730)	$ 102,914,687	$ (323,138,291)
Total Stockholders' Equity (shares)		80,763,350		80,763,350
Net (loss)/income	(1,205,827)		388,050,413	$ (2,738,542)	369,416,894
Issuance of common stock upon exercise of stock options			252,679	0	252,679
Issuance of common stock upon vesting of RSUs and exercise of stock-settled appreciation rights			0	0	0
Issuance of common stock upon exercise of warrants	0		6,007,847	1,172,801	6,007,847
Issuance of common stock				0
Payment of common stock tendered for employee stock-based compensation tax obligations	(143,220)		(1,695,962)	(199,810)	(1,708,290)
Cumulative effect of accounting change						$ (223,313)
Stock-based compensation	$ 761,096		1,176,558	$ 1,717,380	1,866,279
Total Stockholders' Equity (shares)	81,074,280			81,074,280
Total Stockholders' Equity	$ 102,866,516		52,473,805	$ 102,866,516	52,473,805
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Stockholders' Equity	$ 8,105	$ 8,076	$ 7,916	$ 8,076	$ 7,904
Total Stockholders' Equity (shares)	81,046,524	80,763,350	79,160,058	80,763,350	79,039,000
Issuance of common stock upon exercise of stock options (shares)			395,663	9,769	408,698
Issuance of common stock upon exercise of stock options			$ 39	$ 1	$ 41
Issuance of common stock upon vesting of RSUs and exercise of stock-settled appreciation rights (shares)			227,287	121,771	337,084
Issuance of common stock upon vesting of RSUs and exercise of stock-settled appreciation rights			$ 23	$ 12	$ 33
Issuance of common stock upon exercise of warrants (shares)	53,332		760,625	159,782	760,625
Issuance of common stock upon exercise of warrants	$ 5		$ 76	$ 16	$ 76
Issuance of common stock (shares)				53,332
Issuance of common stock				$ 5
Payment of common stock tendered for employee stock-based compensation tax obligations (shares)	(25,576)		(223,098)	(33,724)	(224,872)
Payment of common stock tendered for employee stock-based compensation tax obligations	$ (3)		$ (22)	$ (3)	$ (22)
Total Stockholders' Equity (shares)	81,074,280		80,320,535	81,074,280	80,320,535
Total Stockholders' Equity	$ 8,107		$ 8,032	$ 8,107	$ 8,032
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Stockholders' Equity	220,770,338	$ 218,697,872	214,906,962	218,697,872	214,229,581
Issuance of common stock upon exercise of stock options			252,640	(1)	252,638
Issuance of common stock upon vesting of RSUs and exercise of stock-settled appreciation rights			(23)	(12)	(33)
Issuance of common stock upon exercise of warrants	(5)		6,007,771	1,172,785	6,007,771
Issuance of common stock				(5)
Payment of common stock tendered for employee stock-based compensation tax obligations	(143,217)		(1,695,940)	(199,807)	(1,708,268)
Stock-based compensation	761,096		1,176,558	1,717,380	1,866,279
Total Stockholders' Equity	221,388,212		220,647,968	221,388,212	220,647,968
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Stockholders' Equity	(117,323,976)	(115,791,261)	(556,232,608)	(115,791,261)	(537,375,776)
Net (loss)/income	(1,205,827)		388,050,413		369,416,894
Cumulative effect of accounting change						$ (223,313)
Stock-based compensation		0	0	0	0
Total Stockholders' Equity	(118,529,803)		(168,182,195)	(118,529,803)	(168,182,195)
Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Stockholders' Equity	0	0	0	0	0
Stock-based compensation		$ 0	0	0	0
Total Stockholders' Equity	$ 0		$ 0	$ 0	$ 0