Long-Term Debt - Additional Information (Detail) - USD ($)	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014
Debt Instrument [Line Items]
Financial covenants amount	$ 50,000,000
Interest rate description	Borrowings under the Facility bear interest, at the election of the Company, at the London Interbank Offered Rate (“LIBOR”) plus the applicable margin or the base rate plus the applicable margin. The base rate is the highest of (i) the published prime rate, (ii) the federal funds rate plus 1.50%, or (iii) one month LIBOR plus 1.50%. The applicable margin is based on a percentage per annum determined in accordance with a specified pricing grid based on the total funded debt to adjusted EBITDA ratio. For LIBOR loans, the applicable margin will range from 0.50% to 1.50% per annum, while for base rate loans the applicable margin will range from 0.00% to 0.25% per annum. The Company is required to pay a quarterly commitment fee of 0.25% to 0.35% on the Facility’s average daily unused commitments based on the Company’s funded debt to adjusted EBITDA ratio.
Covenant description	The financial covenants include a maximum total funded debt to adjusted EBITDA ratio and a minimum adjusted EBITDA. As of April 30, 2015, the Company is in compliance with its financial covenants. In addition, there is a domestic liquidity requirement that the Company maintain $50.0 million in unrestricted cash and/or marketable securities (excluding any marketable securities that are held in trust for the settlement of the Company’s obligation under certain deferred compensation plans) as a condition to consummating permitted acquisitions, paying dividends to our shareholders and share repurchases of our common stock.
Value of common shares repurchases permitted, dividends paid and permitted acquisitions for any fiscal year	$ 125,000,000
Dividend payable subject to certain conditions	50,000,000
Long-term debt	$ 0	$ 0
Minimum
Debt Instrument [Line Items]
Quarterly Commitment Fees on the Facility's unused commitments	0.25%
Maximum
Debt Instrument [Line Items]
Quarterly Commitment Fees on the Facility's unused commitments	0.35%
Federal Funds Rate
Debt Instrument [Line Items]
Applicable margin on variable interest rate	1.50%
London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Applicable margin on variable interest rate	1.50%
London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Applicable margin on variable interest rate	0.50%
London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Applicable margin on variable interest rate	1.50%
Base Rate Loans | Minimum
Debt Instrument [Line Items]
Applicable margin on variable interest rate	0.00%
Base Rate Loans | Maximum
Debt Instrument [Line Items]
Applicable margin on variable interest rate	0.25%
Standby Letters of Credit
Debt Instrument [Line Items]
Long-term debt arrangement	$ 2,800,000	2,800,000
Revolving Credit Facility
Debt Instrument [Line Items]
Senior Unsecured Revolving Facility, maximum borrowing capacity	75,000,000
Senior Unsecured Revolving Facility, additional borrowing capacity	$ 50,000,000
Senior Unsecured Revolving Facility, maturity date	Jan. 18, 2018
Revolving Credit Facility | Letter of Credit
Debt Instrument [Line Items]
Senior Unsecured Revolving Facility, maximum borrowing capacity	$ 15,000,000
Other Financial Institutions | Standby Letters of Credit
Debt Instrument [Line Items]
Long-term debt arrangement	1,600,000	1,500,000
Csv Of Coli Contracts
Debt Instrument [Line Items]
Outstanding policy loans	$ 69,600,000	$ 72,900,000
Csv Of Coli Contracts | Minimum
Debt Instrument [Line Items]
Interest payable fixed and variable rates	4.76%
Csv Of Coli Contracts | Maximum
Debt Instrument [Line Items]
Interest payable fixed and variable rates	8.00%