Related Party Transactions (Details)		1 Months Ended	3 Months Ended			6 Months Ended
	Jan. 06, 2018 shares	Dec. 31, 2017 USD ($) shares	Jun. 30, 2019 USD ($) agreement	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2019 USD ($) director agreement	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Mar. 07, 2017 shares	Sep. 30, 2016 USD ($) shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of exclusive channel collaboration agreements (agreement) | agreement			2			2
Related party payable			$ 3,815,000			$ 3,815,000		$ 100,000
Research and development expense			600,000	$ 1,415,000		2,543,000	$ 3,060,000
Common stock issued (shares) | shares	409,091
Warrants Issued With September 2016 Convertible Notes
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants issued to purchase common stock (in shares) | shares											1,205,840
Affiliated Entity
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expenses for work performed			100,000	300,000			300,000
Related party payable			3,800,000			3,800,000		$ 100,000
Research and development expense			$ (4,000)	106,000		$ 40,000	(197,000)
Shareholder ownership percentage of related party in affiliate, more than			50.00%			50.00%
Shareholder ownership percentage			17.00%			17.00%
Affiliated Entity | 2017 Private Placement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants issued to purchase common stock (in shares) | shares		545,456								259,176
Preferred stock, shares issued (shares) | shares										3,016
Common stock issued (shares) | shares		545,456
Affiliated Entity | Warrants Issued With September 2016 Convertible Notes
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants issued to purchase common stock (in shares) | shares											450,835
Affiliated Entity | Convertible Debt
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Convertible debt principal											$ 6,762,500
Affiliated Entity | Direct Expenses for Work Performed
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expenses for work performed			$ 10,000	100,000
Affiliated Entity | Pass-through Costs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expenses for work performed			90,000	$ 200,000
Affiliated Entity | CCP Milestone Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty and milestone payments incurred						$ 3,800,000
Expenses for work performed						3,800,000
Affiliated Entity | 2012 ECC Dispute
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Related party payable		$ 700,000	$ 200,000			$ 200,000			$ 200,000
Research and development expense					$ 1,100,000		$ 1,400,000
Due to related parties, reduction from prior period		$ 500,000
Director
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of directors (director) | director						2