Subsequent Events (Details) - USD ($)		1 Months Ended			3 Months Ended
	Apr. 02, 2018	May 31, 2018	Apr. 30, 2018	Oct. 31, 2017	Jun. 30, 2018
Private Placement
Subsequent Event [Line Items]
Number of shares issued (in shares)				138,361
Net proceeds from sale of shares				$ 2,000,000
RSL | Private Placement | Subsequent Event
Subsequent Event [Line Items]
Number of shares issued (in shares)	1,110,015
Price of shares (in USD per share)	$ 20.27
Gross proceeds from sale of shares			$ 22,500,000
Cowen and Company, LLC | Private Placement | Subsequent Event
Subsequent Event [Line Items]
Aggregate offering price	$ 100,000,000
Cowen and Company, LLC | Private Placement | Scenario, Forecast | Subsequent Event
Subsequent Event [Line Items]
Number of shares issued (in shares)					2,767,129
Price of shares (in USD per share)					$ 21.47
Net proceeds from sale of shares					$ 57,600,000
Commercial Manufacturing and Supply Agreement with Takeda | Subsequent Event
Subsequent Event [Line Items]
Agreement term		5 years
Automatic renewal term		1 year
Termination notice term		12 months
Termination notice term, uncured material breach		90 days
Termination notice term, open purchase orders filed		180 days