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           Orange-Co Acquisition (Schedule of Purchase Consideration) (Details) (USD $) 
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        3 Months Ended | 0 Months Ended | |
|---|---|---|---|
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           Dec. 31, 2014 
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           Dec. 31, 2013 
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           Dec. 02, 2014 
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| Business Acquisition [Line Items] | |||
| Cash proceeds from sugarcane disposition | $ 265,063,000us-gaap_PaymentsToAcquireBusinessesGross | ||
| Orange-Co Acquisition [Member] | |||
| Business Acquisition [Line Items] | |||
| Cash proceeds from sugarcane disposition | 
97,126,000us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = alco_OrangeCoAcquisitionMember  | 
        
147,500,000us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = alco_OrangeCoAcquisitionMember  | 
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| Total purchase consideration | 
265,063,000us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = alco_OrangeCoAcquisitionMember  | 
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| Orange-Co Acquisition [Member] | Line of Credit [Member] | |||
| Business Acquisition [Line Items] | |||
| Liabilities incurred | 
27,775,000us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred / us-gaap_BusinessAcquisitionAxis = alco_OrangeCoAcquisitionMember / us-gaap_LongtermDebtTypeAxis = us-gaap_LineOfCreditMember  | 
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| Orange-Co Acquisition [Member] | Term Loan [Member] | |||
| Business Acquisition [Line Items] | |||
| Liabilities incurred | 
$ 140,162,000us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred / us-gaap_BusinessAcquisitionAxis = alco_OrangeCoAcquisitionMember / us-gaap_LongtermDebtTypeAxis = us-gaap_LoansPayableMember  | 
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- Details 
          
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- Definition 
          Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
          
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