Stock-Based Compensation - Summarized Activity Related to Director Deferred Compensation Shares (Detail) - Directors [Member] - Deferred Compensation Share Equivalent Units [Member] shares in Thousands	Apr. 30, 2020 $ / shares shares
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Number of Shares, Outstanding, Beginning balance | shares	114
Number of Shares, Outstanding, Ending balance | shares	114
Weighted-Average Grant Date Fair Value, Beginning balance | $ / shares	$ 55.52
Weighted-Average Grant Date Fair Value, Ending balance | $ / shares	$ 55.99