Annual report pursuant to Section 13 and 15(d)

Commitments And Contingencies - Additional Information (Detail)

Commitments And Contingencies - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Apr. 30, 2017
Apr. 30, 2016
Apr. 30, 2015
Commitments And Contingent Liabilities [Line Items]      
Lease expiration date 2030    
Total rental expense $ 56.8 $ 45.5 $ 38.0
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 during the term of their employment, and for a certain period after their employment ends.