Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt - Additional Information (Detail)

v3.2.0.727
Long-Term Debt - Additional Information (Detail) - USD ($)
Jun. 05, 2015
Jul. 31, 2015
Apr. 30, 2015
Debt Instrument [Line Items]      
Long-term debt   $ 0 $ 0
Amendment of Credit Facility      
Debt Instrument [Line Items]      
Value of common shares repurchases permitted, dividends paid and permitted acquisitions for any fiscal year $ 125,000,000    
Value of common shares repurchases permitted and dividends paid for any fiscal year 75,000,000    
Amendment of Credit Facility | Cash, Cash Equivalents and Marketable Securities      
Debt Instrument [Line Items]      
Financial covenants amount $ 50,000,000    
Amendment of Credit Facility | Minimum      
Debt Instrument [Line Items]      
Quarterly Commitment Fees on the Facility's unused commitments 0.25%    
Amendment of Credit Facility | Maximum      
Debt Instrument [Line Items]      
Quarterly Commitment Fees on the Facility's unused commitments 0.40%    
Amendment of Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum      
Debt Instrument [Line Items]      
Applicable margin on variable interest rate 0.875%    
Amendment of Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum      
Debt Instrument [Line Items]      
Applicable margin on variable interest rate 1.75%    
Amendment of Credit Facility | Base Rate Loans | Minimum      
Debt Instrument [Line Items]      
Applicable margin on variable interest rate 0.00%    
Amendment of Credit Facility | Base Rate Loans | Maximum      
Debt Instrument [Line Items]      
Applicable margin on variable interest rate 0.75%    
Standby Letters of Credit      
Debt Instrument [Line Items]      
Long-term debt arrangement   2,800,000 2,800,000
Other Financial Institutions | Standby Letters of Credit      
Debt Instrument [Line Items]      
Long-term debt arrangement   $ 1,400,000 $ 1,600,000
Revolving Credit Facility | Amendment of Credit Facility      
Debt Instrument [Line Items]      
Revolving credit facility, maximum borrowing capacity $ 150,000,000    
Revolving credit facility, additional optional increase to maximum borrowing capacity $ 50,000,000    
Revolving credit facility, extended maturity date Jun. 03, 2020    
Revolving Credit Facility | Letter of Credit | Amendment of Credit Facility      
Debt Instrument [Line Items]      
Revolving credit facility, maximum borrowing capacity $ 15,000,000