Stockholders' Equity - Issuances Related to the License Agreement (Details)				6 Months Ended
	Mar. 02, 2018 $ / shares shares	Oct. 24, 2017 shares	Sep. 29, 2017 item shares	Jun. 30, 2018 USD ($)
Common Stock Offering [Abstract]
Issuance of common stock in connection with equity offering (in shares)	20,535,714
Share price | $ / shares	$ 4.20
Net proceeds from issuance of stock | $				$ 80,900,581
Underwriting discounts and commissions | $				5,200,000
Offering expenses | $				$ 100,000
Issuances Related to the License Agreement
Number of shares of common stock filed on registration statement per Registration Rights Agreement		6,000,000
License Agreement | ABX
Issuances Related to the License Agreement
Common stock issued per agreement			2,000,000
Number Of Warrants Issued Per Agreement | item			2
Aggregate number of common stock shares that may be purchased by exercise of warrants			4,000,000
Number of warrants exercised | item			1
Stock Issued During Period Shares Warrant Exercise			3,278,000
License Agreement | ABX | Maximum
Issuances Related to the License Agreement
Aggregate number of common stock shares that may be purchased by exercise of warrants			4,000,000