Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt (Schedule of Outstanding Debt) (Details)

v2.4.1.9
Long-Term Debt (Schedule of Outstanding Debt) (Details) (USD $)
6 Months Ended
Mar. 31, 2015
Sep. 30, 2014
Jun. 30, 2014
Debt Instrument [Line Items]      
Total $ 210,011,000us-gaap_LongTermDebt $ 61,640,000us-gaap_LongTermDebt  
Long-term debt, current portion 4,511,000us-gaap_LongTermDebtCurrent 3,196,000us-gaap_LongTermDebtCurrent  
Long-term debt, net of current portion 205,500,000us-gaap_LongTermDebtNoncurrent 58,444,000us-gaap_LongTermDebtNoncurrent  
Metropolitan Life Insurance Company and New England Life Insurance Company fixed rate term loans in the original principal amount of $125 million [Member]      
Debt Instrument [Line Items]      
Total 114,688,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_FixedRateTermLoanMember
    
Principal amount of debt 125,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= alco_FixedRateTermLoanMember
   
Fixed interest rate 4.15%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= alco_FixedRateTermLoanMember
   
Metropolitan Life Insurance Company and New England Life Insurance Company variable rate term loans in the original principal amounts of $57.5 million [Member]      
Debt Instrument [Line Items]      
Total 56,781,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_VariableRateTermLoanMember
    
Principal amount of debt 57,500,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= alco_VariableRateTermLoanMember
   
Effective interest rate 1.75%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= alco_VariableRateTermLoanMember
   
Metropolitan Life Insurance Company term loan [Member]      
Debt Instrument [Line Items]      
Total 500,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_CitreeTermLoanMember
    
Fixed interest rate 5.49%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= alco_CitreeTermLoanMember
   
Amount of future advance 4,500,000alco_DebtInstrumentAmountOfFutureAdvance
/ us-gaap_DebtInstrumentAxis
= alco_CitreeTermLoanMember
   
Rabo Agrifinance, Inc. variable rate term loan [Member]      
Debt Instrument [Line Items]      
Total    34,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_RevolvingLineOfCreditMember
 
Effective interest rate 2.40%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= alco_RevolvingLineOfCreditMember
   
Prudential Mortgage Capital Company, LLC fixed rate term loans (5.35%) [Member]      
Debt Instrument [Line Items]      
Total 26,970,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_PrudentialMortgageCapitalCompanyLlcFixedRateTermLoans5Point35Member
27,550,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_PrudentialMortgageCapitalCompanyLlcFixedRateTermLoans5Point35Member
27,550,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_PrudentialMortgageCapitalCompanyLlcFixedRateTermLoans5Point35Member
Fixed interest rate 5.35%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= alco_PrudentialMortgageCapitalCompanyLlcFixedRateTermLoans5Point35Member
   
Prudential Mortgage Capital Company, LLC fixed rate term loan (3.85%) [Member]      
Debt Instrument [Line Items]      
Total 5,500,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_PrudentialMortgageCapitalCompanyLlcFixedRateTermLoan3Point85Member
    
Fixed interest rate 3.85%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= alco_PrudentialMortgageCapitalCompanyLlcFixedRateTermLoan3Point85Member
   
Prudential Mortgage Capital Company, LLC fixed rate term loan (3.45%) [Member]      
Debt Instrument [Line Items]      
Total 5,500,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_PrudentialMortgageCapitalCompanyLlcFixedRateTermLoan3Point45Member
    
Fixed interest rate 3.45%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= alco_PrudentialMortgageCapitalCompanyLlcFixedRateTermLoan3Point45Member
   
Note Payable to Financing Company [Member]      
Debt Instrument [Line Items]      
Total $ 72,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_NotePayableToFinancingCompanyMember
$ 90,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= alco_NotePayableToFinancingCompanyMember