Acquisitions - Additional Information (Detail) - USD ($)		3 Months Ended
	Jun. 16, 2015	Aug. 01, 2015	Jul. 26, 2014	Apr. 25, 2015
Business Acquisition [Line Items]
Goodwill		$ 817,481,000		$ 299,924,000
Revenues		1,142,870,000	$ 938,956,000
Operating income		62,177,000	$ 65,996,000
Tax impact of repatriation of foreign earnings		11,800,000
Animal Health International [Member]
Business Acquisition [Line Items]
Business acquisition cash paid	$ 1,100,000,000
Identifiable net assets acquired	$ 589,833,000
Revision period after valuation completion for provisional amounts	1 year
Deferred tax asset	$ 2,569,000
Deferred tax liability	177,789,000
Goodwill	517,871,000
Goodwill recognized, deductible for income tax purpose	0
Deferred taxes recorded related to goodwill	0
Revenues		171,922,000
Operating income		$ 1,653,000
Animal Health International [Member] | Term Loan [Member]
Business Acquisition [Line Items]
Unsecured term loan	1,000,000,000
Animal Health International [Member] | Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Unsecured revolving line of credit	$ 500,000,000