Convertible Preferred Shares (Details)	1 Months Ended			9 Months Ended
	May 31, 2017 shares	Feb. 28, 2017 USD ($) item $ / shares shares	Oct. 31, 2016 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares shares	Oct. 01, 2017 $ / shares	May 11, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares	Jul. 31, 2016 $ / shares	Feb. 29, 2016 $ / shares
Preferred Shares
Preferred stock, shares authorized | shares	10,000,000			0		10,000,000	11,242,172
Preferred stock, par value | $ / shares				$ 0		$ 0	$ 0
Fair value of common share | $ / shares								$ 7.70	$ 7.00
Net proceeds				$ 40,000,000
Accretion of beneficial conversion feature on Series A preferred shares				$ (12,006,000)
Series A Convertible Preferred Shares
Preferred Shares
Preferred stock, shares authorized | shares				11,242,172
Preferred stock issued and sold | shares		4,305,182	4,305,209	4,305,182
Number of placement agents | item		2
Fair value of common share | $ / shares		$ 9.2911	$ 9.2911
Net proceeds		$ 38,636,000	$ 37,295,000
Offering costs		2,606,000	2,705,000
Issuance of common stock, issuance costs		1,364,000	1,730,000	$ 1,334,000
Issuance of Series A preferred shares as payment of offering costs		105,009	105,010
Value of Preferred Share			$ 975,000
Accretion of beneficial conversion feature on Series A preferred shares		$ (2,406,000)		$ 12,006,000
Maximum price for fair value of the underlying common shares | shares		9.85
Shares issued on conversion of preferred stock | shares	9,358,560
Shares issued on conversion of preferred stock to common stock				1
Shares issued on conversion of preferred stock to common stock if company fails to initiate Phase 3				0.001
Share Price if company fails to initiate Phase 3 | $ / shares					7.0613
Dividend rate (as a percent)				8.00%
Series A Convertible Preferred Shares | Minimum
Preferred Shares
Net proceeds				$ 50,000,000
Series A Convertible Preferred Shares | AstraZeneca
Preferred Shares
Preferred stock issued and sold | shares			538,150
Fair value of common share | $ / shares			$ 9.2911
Aggregate fair value			$ 5,000,000
Series A Convertible Preferred Shares | Placement agents
Preferred Shares
Fair value of common share | $ / shares		$ 11.83
Value of Preferred Share		$ 1,242,000