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Goodwill and Other Intangible Assets - Narrative (Details)
 12 Months Ended
Feb. 01, 2018
reporting_unit
Apr. 30, 2018
USD ($)
Apr. 30, 2017
USD ($)
Apr. 30, 2016
USD ($)
Goodwill and Intangible Assets [Line Items]        
Goodwill, Impaired, Accumulated Impairment Loss   $ 145,000,000 $ 0  
Amortization expense for finite-lived intangible assets   $ 204,800,000 205,900,000 $ 204,700,000
Weighted-average useful life of the finite-lived intangible assets   22 years    
Estimated amortization expense for 2019   $ 205,100,000    
Estimated amortization expense for 2020   200,400,000    
Estimated amortization expense for 2021   198,800,000    
Estimated amortization expense for 2022   193,400,000    
Estimated amortization expense for 2023   186,000,000    
Number of reporting units | reporting_unit 7      
Impairment charges   176,900,000    
Goodwill impairment charge   145,000,000 [1] 0 0
Other intangible assets impairment charges   $ 31,900,000 $ 133,200,000 $ 0
Customer and Contractual Relationships [Member]        
Goodwill and Intangible Assets [Line Items]        
Weighted-average useful life of the finite-lived intangible assets   23 years    
Patents And Technology [Member]        
Goodwill and Intangible Assets [Line Items]        
Weighted-average useful life of the finite-lived intangible assets   14 years    
Trademarks [Member]        
Goodwill and Intangible Assets [Line Items]        
Weighted-average useful life of the finite-lived intangible assets   16 years    
U.S. Retail Pet Foods [Member]        
Goodwill and Intangible Assets [Line Items]        
Goodwill impairment charge [1]   $ 145,000,000    
[1] There have been no goodwill impairment charges recognized in prior periods.