Subsequent Events - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Jul. 19, 2016	Jun. 15, 2016	Apr. 30, 2016	Apr. 30, 2015	Mar. 11, 2015
Subsequent Event [Line Items]
Common stock, par value (in dollars per share)			$ 0.001	$ 0.001	$ 0.001
Issuance of common stock			$ 44	$ 0
Offering-related expense			$ 18	$ 0
Shares exchange during period (in shares)			1,656,073
Exchanges, weighted average exercise price (in dollars per share)			$ 4.92
Shares granted (in shares)			343,749	1,763,381
Grants in period, weighted average exercise price (in usd per share)			$ 5.33	$ 7.92
Subsequent Event [Member]
Subsequent Event [Line Items]
Issuance of common stock		$ 4,300
Offering-related expense		$ 750
Shares exchange during period (in shares)	1,793,781
Shares granted (in shares)	1,568,191
Grants in period, weighted average exercise price (in usd per share)	$ 2.10
Minimum [Member]
Subsequent Event [Line Items]
Exchanges, weighted average exercise price (in dollars per share)			15.96
Minimum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Exchanges, weighted average exercise price (in dollars per share)	4.55
Maximum [Member]
Subsequent Event [Line Items]
Exchanges, weighted average exercise price (in dollars per share)			$ 5.64
Maximum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Exchanges, weighted average exercise price (in dollars per share)	$ 6.96
Common Stock [Member] | Subsequent Event [Member]
Subsequent Event [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
Common Stock [Member] | Over-Allotment Option [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Shares issued in offering (in shares)		258,749