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Derivative Financial Instruments (Details) (USD $)
In Thousands, unless otherwise specified
 9 Months Ended
Feb. 28, 2015
bu
May 31, 2014
Derivatives, Fair Value [Line Items]    
Derivative, fair value $ 1,242us-gaap_DerivativeFairValueOfDerivativeNet $ 1,255us-gaap_DerivativeFairValueOfDerivativeNet
Corn Commodity [Member]    
Derivatives, Fair Value [Line Items]    
Derivative, fair value 635us-gaap_DerivativeFairValueOfDerivativeNet
/ us-gaap_DerivativeInstrumentRiskAxis
= calm_CornCommodityMember		  
Underlying, derivative volume 4,675,000calm_UnderlyingDerivativeVolume1
/ us-gaap_DerivativeInstrumentRiskAxis
= calm_CornCommodityMember		  
Soybean Meal Commodity [Member]    
Derivatives, Fair Value [Line Items]    
Derivative, fair value $ 607us-gaap_DerivativeFairValueOfDerivativeNet
/ us-gaap_DerivativeInstrumentRiskAxis
= calm_SoybeanMealCommodityMember		  
Underlying, derivative mass 49,000calm_UnderlyingDerivativeMass1
/ us-gaap_DerivativeInstrumentRiskAxis
= calm_SoybeanMealCommodityMember		  
Maximum [Member]    
Derivatives, Fair Value [Line Items]    
Term of contract 6 months