Commitments And Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Commitments And Contingent Liabilities [Line Items]
Lease expiration date	2026
Total rental expense	$ 45.5	$ 38.0	$ 39.6
Employment agreements	The Company has a policy of entering into offer letters of employment or letters of promotion with vice presidents which provide for an annual base salary and discretionary and incentive bonus payments. Certain key vice presidents who typically have been employed by the Company for several years may also have a standard form employment agreement. Upon termination without cause, the Company is required to pay the amount of severance due under the employment agreement, if any. The Company also requires its vice presidents to agree in their employment letters and their employment agreement, if applicable, not to compete with the Company both during the term of their employment, and for a period of up to two years after their employment ends. For a period of two years after their employment with the Company, former vice presidents are prohibited from soliciting employees of the Company for employment outside of the Company.