Acquisitions - Summary of Total Purchase Price Consideration and Preliminary Fair Value of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	3 Months Ended
	Aug. 01, 2015	Jan. 30, 2016	Jun. 16, 2015	Apr. 25, 2015
Business Acquisition [Line Items]
Goodwill		$ 815,316		$ 299,924
Animal Health International [Member]
Business Acquisition [Line Items]
Total purchase price consideration	$ 1,106,583
Receivables	161,427
Inventory	195,367
Prepaid expenses and other current assets	33,005
Property and equipment	44,178
Identifiable intangibles	434,300		$ 434,300
Other long-term assets	40,869
Total assets acquired	909,146
Accounts payable	122,129
Accrued liabilities and other current liabilities	21,015
Deferred tax liability	177,789
Total liabilities assumed	320,933
Identifiable net assets acquired	588,213
Goodwill	518,370
Net assets acquired	$ 1,106,583