Debt - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Nov. 21, 2014	Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2015	Oct. 31, 2014	Apr. 30, 2015
Debt Instrument [Line Items]
Amortization of deferred financing costs				$ 118	$ 0
Credit facility
Debt Instrument [Line Items]
Fees capitalized related to the amended and restated credit facility				700
Revolving credit facility
Debt Instrument [Line Items]
Amortization of deferred financing costs		$ 100	$ 0	100	$ 0
Revolving credit facility | Loan agreement
Debt Instrument [Line Items]
Letters of credit outstanding, Amount		9,300		$ 9,300
Revolving credit facility | Credit facility
Debt Instrument [Line Items]
Revolving line of credit with a borrowing capacity	$ 70,000
Revolving letter of credit with a borrowing capacity	$ 15,000
Loan and security agreement, expiration date				Nov. 21, 2017
Revolving credit facility | Unused lines of credit | Credit facility
Debt Instrument [Line Items]
Credit facility, remaining borrowing capacity		$ 3,700		$ 3,700		$ 3,700
Revolving credit facility | Daily adjusting LIBOR rate | Credit facility
Debt Instrument [Line Items]
Interest above daily adjusting LIBOR rate	3.50%
Revolving credit facility | Swingline Loan | Credit facility
Debt Instrument [Line Items]
Revolving line of credit with a borrowing capacity	$ 3,000