Common Stock - Narrative (Details) - USD ($)				9 Months Ended
	Jan. 24, 2017	Jul. 06, 2016	Jun. 15, 2016	Jan. 31, 2017	Jan. 31, 2016	Apr. 30, 2016
Class of Stock [Line Items]
Common stock, par value (in dollars per share)				$ 0.001		$ 0.001
Issuance of common stock			$ 4,300,000	$ 4,340,000	$ 0
Offering-related expense			$ 742,000	$ 0	$ 18,000
Shares issued in relation to consulting services	3,247	3,896
Shares issued in relation to consulting services, value	$ 11,852	$ 8,688
Common Stock [Member]
Class of Stock [Line Items]
Shares issued in offering (in shares)			2,000,000
Common stock, par value (in dollars per share)			$ 0.001
Share price (in usd per share)			$ 2.25
Over-Allotment Option [Member] | Common Stock [Member]
Class of Stock [Line Items]
Shares issued in offering (in shares)			258,749