Debt - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Nov. 21, 2014	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015	Apr. 30, 2016
Debt Instrument [Line Items]
Amortization of deferred financing costs				$ 118	$ 118
Revolving line of credit		$ 37,000		$ 37,000		$ 42,000
Revolving credit facility
Debt Instrument [Line Items]
Revolving line of credit with a borrowing capacity	$ 70,000
Loan and security agreement, expiration date				Nov. 21, 2017
Letters of credit outstanding, Amount		9,300		$ 9,300
Fees capitalized related to the amended and restated credit facility				700
Amortization of deferred financing costs		100	$ 100
Repayments of Debt				5,000
Long-term Line of Credit		37,000		37,000
Revolving credit facility | Unused lines of credit
Debt Instrument [Line Items]
Credit facility, remaining borrowing capacity		$ 23,700		$ 23,700
Revolving credit facility | Daily adjusting LIBOR rate
Debt Instrument [Line Items]
Interest above daily adjusting LIBOR rate	3.50%
Revolving credit facility | Swingline Loan
Debt Instrument [Line Items]
Revolving line of credit with a borrowing capacity	$ 3,000
Revolving credit facility | Letter of Credit [Member]
Debt Instrument [Line Items]
Revolving letter of credit with a borrowing capacity	$ 15,000