Stockholders' Equity - Common Stock Transactions (Details) - USD ($)	1 Months Ended	2 Months Ended	3 Months Ended				12 Months Ended			24 Months Ended
	Jul. 31, 2018	Mar. 04, 2020	Mar. 04, 2020	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 16, 2019	Aug. 30, 2019	Jun. 30, 2017
Sales of Stock
Proceeds from the issuance of common stock, net of issuance costs							$ 45,187,070	$ 29,937,505	$ 57,293,041
2017 Sales Agreement
Sales of Stock
Maximum aggregate value of common stock available for offering												$ 50,000,000
Shares issued				2,082,031	3,439,523				296,594
Weighted average selling price per share				$ 13.50	$ 5.44				$ 10.74
Gross proceeds from issuance of common stock				$ 28,100,000	$ 18,700,000				$ 3,200,000	$ 50,000,000
Proceeds from the issuance of common stock, net of issuance costs				$ 27,000,000	$ 18,100,000				$ 3,000,000
Follow On Public Offering
Sales of Stock
Shares issued	4,062,500					3,220,000
Weighted average selling price per share	$ 8.00
Offering price per share	$ 8.00					$ 18.00
Gross proceeds from issuance of common stock	$ 32,500,000					$ 58,000,000
Proceeds from the issuance of common stock, net of issuance costs	$ 29,900,000					$ 54,200,000
2019 Sales Agreement
Sales of Stock
Maximum aggregate value of common stock available for offering											$ 75,000,000
Shares issued		339,790	353,171				13,381
Weighted average selling price per share		$ 5.15	$ 5.22				$ 7.00
Gross proceeds from issuance of common stock		$ 1,700,000	$ 1,800,000				$ 100,000
Proceeds from the issuance of common stock, net of issuance costs		$ 1,500,000	$ 1,600,000				$ 100,000