Shareholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Oct. 29, 2016	Oct. 29, 2016	Apr. 30, 2016	Oct. 31, 2015	Oct. 20, 2015
Class of Stock [Line Items]
Stock repurchased, shares	878,195	1,708,778
Stock repurchased, value	$ 10,045,000	$ 19,788,000
Stock repurchase program, remaining authorized repurchase amount	$ 3,494,000	$ 3,494,000
Treasury stock, shares	39,741,000	39,741,000	37,941,000	34,961,000
Treasury stock, at cost	$ 1,131,319,000	$ 1,131,319,000	$ 1,110,438,000	$ 1,081,803,000
Maximum
Class of Stock [Line Items]
Number of shares authorized to be repurchase					$ 50,000,000
Stock Repurchase Program
Class of Stock [Line Items]
Treasury stock, shares	39,741,262	39,741,262
Treasury stock, at cost	$ 1,084,812,000	$ 1,084,812,000