| 
           Disclosures about reportable segments (Details) (USD $) In Thousands, unless otherwise specified 
         | 
        3 Months Ended | 
         | 
      
| 
           Dec. 31, 2014 
         | 
        
           Dec. 31, 2013 
         | 
        
           Sep. 30, 2014 
         | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total operating revenue | 
        
$ 16,158us-gaap_Revenues
 | 
        
$ 14,989us-gaap_Revenues
 | 
         
 | 
      
| Total operating expenses | 
        
13,014us-gaap_CostOfRevenue
 | 
        
12,418us-gaap_CostOfRevenue
 | 
         
 | 
      
| Gross profit | 
        
3,144us-gaap_GrossProfit
 | 
        
2,571us-gaap_GrossProfit
 | 
         
 | 
      
| Total capital expenditures | 
        
2,048us-gaap_PaymentsToAcquireProductiveAssets
 | 
        
6,539us-gaap_PaymentsToAcquireProductiveAssets
 | 
         
 | 
      
| Total depreciation, depletion and amortization | 
        
1,841us-gaap_DepreciationDepletionAndAmortization
 | 
        
2,502us-gaap_DepreciationDepletionAndAmortization
 | 
         
 | 
      
| Total assets | 
        
411,449us-gaap_Assets
 | 
         
 | 
        
203,567us-gaap_Assets
 | 
      
| Citrus Groves Segment [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total operating revenue | 
        
12,898us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
        
5,633us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
         
 | 
      
| Total operating expenses | 
        
10,059us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
        
3,898us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
         
 | 
      
| Gross profit | 
        
2,839us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
        
1,735us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
         
 | 
      
| Total capital expenditures | 
        
1,569us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
        
1,943us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
         
 | 
      
| Total depreciation, depletion and amortization | 
        
1,256us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
        
529us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
         
 | 
      
| Agricultural Supply Chain Management [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total operating revenue | 
        
1,183us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
        
2,106us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
         
 | 
      
| Total operating expenses | 
        
1,371us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
        
2,325us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
         
 | 
      
| Gross profit | 
        
(188)us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
        
(219)us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
         
 | 
      
| Total capital expenditures | 
        
210us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
        
33us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
         
 | 
      
| Total depreciation, depletion and amortization | 
        
52us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
        
29us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
         
 | 
      
| Improved Farmland [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total operating revenue | 
        
1,092us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
        
6,532us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
         
 | 
      
| Total operating expenses | 
        
791us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
        
5,530us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
         
 | 
      
| Gross profit | 
        
301us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
        
1,002us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
         
 | 
      
| Total capital expenditures | 
          
 | 
        
3,473us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
         
 | 
      
| Total depreciation, depletion and amortization | 
          
 | 
        
1,337us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
         
 | 
      
| Ranch and Conservation [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total operating revenue | 
        
836us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
        
531us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
         
 | 
      
| Total operating expenses | 
        
745us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
        
603us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
         
 | 
      
| Gross profit | 
        
91us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
        
(72)us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
         
 | 
      
| Total capital expenditures | 
        
176us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
        
743us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
         
 | 
      
| Total depreciation, depletion and amortization | 
        
243us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
        
333us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
         
 | 
      
| Other Operations [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total operating revenue | 
        
149us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
        
187us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
         
 | 
      
| Total operating expenses | 
        
48us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
        
62us-gaap_CostOfRevenue / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
         
 | 
      
| Gross profit | 
        
101us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
        
125us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
         
 | 
      
| Total capital expenditures | 
        
15us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
        
4us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
         
 | 
      
| Total depreciation, depletion and amortization | 
        
128us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
        
88us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
         
 | 
      
| Operating Segments [Member] | Citrus Groves Segment [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total assets | 
        
351,247us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
         
 | 
        
67,388us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_CitrusGrovesSegmentMember
 | 
      
| Operating Segments [Member] | Agricultural Supply Chain Management [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total assets | 
        
3,264us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
         
 | 
        
2,498us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_AgriculturalSupplyChainManagementMember
 | 
      
| Operating Segments [Member] | Improved Farmland [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total assets | 
        
225us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
         
 | 
        
57,726us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_ImprovedFarmlandMember
 | 
      
| Operating Segments [Member] | Ranch and Conservation [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total assets | 
        
12,913us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
         
 | 
        
13,920us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_RanchAndConservationMember
 | 
      
| Operating Segments [Member] | Other Operations [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total assets | 
        
31,050us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
         
 | 
        
26,356us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
 | 
      
| Operating Segments [Member] | Intersegment Revenues [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total operating revenue | 
        
1,271us-gaap_Revenues / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_IntersegmentTansactionsSegmentMember
 | 
        
1,153us-gaap_Revenues / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = alco_IntersegmentTansactionsSegmentMember
 | 
         
 | 
      
| Intersegment Eliminations [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total operating revenue | 
        
(1,271)us-gaap_Revenues / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember
 | 
        
(1,153)us-gaap_Revenues / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember
 | 
         
 | 
      
| Non - Segments [Member] | 
         
 | 
         
 | 
         
 | 
      
| Segment Reporting, Revenue Reconciling Item [Line Items] | 
         
 | 
         
 | 
         
 | 
      
| Total capital expenditures | 
        
78us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_ConsolidationItemsAxis = us-gaap_CorporateNonSegmentMember
 | 
        
343us-gaap_PaymentsToAcquireProductiveAssets / us-gaap_ConsolidationItemsAxis = us-gaap_CorporateNonSegmentMember
 | 
         
 | 
      
| Total depreciation, depletion and amortization | 
        
162us-gaap_DepreciationDepletionAndAmortization / us-gaap_ConsolidationItemsAxis = us-gaap_CorporateNonSegmentMember
 | 
        
186us-gaap_DepreciationDepletionAndAmortization / us-gaap_ConsolidationItemsAxis = us-gaap_CorporateNonSegmentMember
 | 
         
 | 
      
| Total assets | 
        
$ 12,749us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_CorporateNonSegmentMember
 | 
         
 | 
        
$ 35,679us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_CorporateNonSegmentMember
 |