Share-Based Payments - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended
	Jul. 19, 2016	Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding, Beginning Balance		2,212,757
Shares, Granted	1,568,191	2,420,681
Shares, Exercised		0
Shares, Forfeited		(421,487)
Shares, Canceled		(1,793,779)
Shares, Expired		(109,468)
Shares, Outstanding, Ending Balance		2,308,704
Shares, Vested and expected to vest		2,308,704
Shares, Exercisable		1,987,719
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Outstanding, Beginning Balance (in usd per share)		$ 5.58
Weighted Average Exercise Price, Granted (in usd per share)	$ 2.10	1.99
Weighted Average Exercise Price, Exercised (in usd per share)		0
Weighted Average Exercise Price, Forfeited (in usd per share)		2.03
Weighted Average Exercise Price, Canceled (in usd per share)		4.92
Weighted Average Exercise Price, Expired (in usd per share)		7.86
Weighted Average Exercise Price, Outstanding, Ending Balance (in usd per share)		2.76
Weighted Average Exercise Price, Vested and expected to vest (in usd per share)		2.76
Weighted Average Exercise Price, Exercisable (in usd per share)		$ 2.97
Weighted Average Remaining Contractual Term, Outstanding, Beginning Balance (in years)		6 years 1 month 6 days
Weighted Average Remaining Contractual Life, Granted (in years)		7 years
Weighted Average Remaining Contractual Term, Outstanding, Ending Balance (in years)		6 years 7 months 1 day
Weighted Average Remaining Contractual Life, Vested and expected to vest (in years)		6 years 7 months 1 day
Weighted Average Remaining Contractual Life, Exercisable (in years)		6 years
Aggregate Intrinsic Value, Outstanding, Beginning Balance		$ 10
Aggregate Intrinsic Value, Granted		6,688
Aggregate Intrinsic Value, Outstanding, Ending Balance		6,201
Aggregate Intrinsic Value, Vested and expected to vest		6,201
Aggregate Intrinsic Value, Exercisable		$ 4,672
Non-Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding, Beginning Balance		51,250
Shares, Granted		0
Shares, Exercised		0
Shares, Forfeited		0
Shares, Canceled		0
Shares, Expired		(1,250)
Shares, Outstanding, Ending Balance		50,000
Shares, Vested and expected to vest		50,000
Shares, Exercisable		33,336
Directors and Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares, Outstanding, Beginning Balance		2,161,507
Shares, Granted		2,420,681
Shares, Exercised		0
Shares, Forfeited		(421,487)
Shares, Canceled		(1,793,779)
Shares, Expired		(108,218)
Shares, Outstanding, Ending Balance		2,258,704
Shares, Vested and expected to vest		2,258,704
Shares, Exercisable		1,954,383