XML 18 R37.htm IDEA: XBRL DOCUMENT v2.4.1.9
Financial Instruments Balance Sheet Location (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Sep. 30, 2014
Derivatives Fair Value [Line Items]    
Derivative, Collateral, Right to Reclaim Cash $ 17,400us-gaap_DerivativeCollateralRightToReclaimCash $ 22,700us-gaap_DerivativeCollateralRightToReclaimCash
Derivative Asset 18,378us-gaap_DerivativeAssets 58,865us-gaap_DerivativeAssets
Derivative Liability, Collateral, Right to Reclaim Cash, Offset 26,100us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset 3,100us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset
Derivative Liability (95,824)us-gaap_DerivativeLiabilities (21,856)us-gaap_DerivativeLiabilities
Regulated Distribution Segment [Member]    
Derivatives Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset 976us-gaap_DerivativeFairValueOfDerivativeAsset
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36,140us-gaap_DerivativeFairValueOfDerivativeAsset
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Derivative Asset, Contract Netting 0ato_DerivativeAssetContractNetting
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0ato_DerivativeAssetContractNetting
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Derivative Asset, Net of Contract Netting 976ato_DerivativeAssetNetofContractNetting
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36,140ato_DerivativeAssetNetofContractNetting
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Derivative, Collateral, Right to Reclaim Cash 0us-gaap_DerivativeCollateralRightToReclaimCash
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0us-gaap_DerivativeCollateralRightToReclaimCash
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Derivative Asset 976us-gaap_DerivativeAssets
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36,140us-gaap_DerivativeAssets
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Derivative Liability, Fair Value, Gross Liability (95,824)us-gaap_DerivativeFairValueOfDerivativeLiability
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(21,856)us-gaap_DerivativeFairValueOfDerivativeLiability
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Derivative Liability, Contract Netting 0ato_DerivativeLiabilityContractNetting
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0ato_DerivativeLiabilityContractNetting
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Derivative Liability, Net of Contract Netting (95,824)ato_DerivativeLiabilityNetofContractNetting
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(21,856)ato_DerivativeLiabilityNetofContractNetting
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Derivative Liability, Collateral, Right to Reclaim Cash, Offset 0us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset
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0us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset
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Derivative Liability (95,824)us-gaap_DerivativeLiabilities
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(21,856)us-gaap_DerivativeLiabilities
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Nonregulated Segment [Member]    
Derivatives Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset 228,486us-gaap_DerivativeFairValueOfDerivativeAsset
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69,023us-gaap_DerivativeFairValueOfDerivativeAsset
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Derivative Asset, Contract Netting (228,486)ato_DerivativeAssetContractNetting
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= ato_NonregulatedSegmentMember
(69,023)ato_DerivativeAssetContractNetting
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Derivative Asset, Net of Contract Netting 0ato_DerivativeAssetNetofContractNetting
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0ato_DerivativeAssetNetofContractNetting
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Derivative, Collateral, Right to Reclaim Cash 17,402us-gaap_DerivativeCollateralRightToReclaimCash
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22,725us-gaap_DerivativeCollateralRightToReclaimCash
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Derivative Asset 17,402us-gaap_DerivativeAssets
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22,725us-gaap_DerivativeAssets
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Derivative Liability, Fair Value, Gross Liability (254,585)us-gaap_DerivativeFairValueOfDerivativeLiability
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(72,056)us-gaap_DerivativeFairValueOfDerivativeLiability
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Derivative Liability, Contract Netting 228,486ato_DerivativeLiabilityContractNetting
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69,023ato_DerivativeLiabilityContractNetting
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Derivative Liability, Net of Contract Netting (26,099)ato_DerivativeLiabilityNetofContractNetting
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(3,033)ato_DerivativeLiabilityNetofContractNetting
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Derivative Liability, Collateral, Right to Reclaim Cash, Offset 26,099us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset
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3,033us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset
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Derivative Liability 0us-gaap_DerivativeLiabilities
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0us-gaap_DerivativeLiabilities
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Designated As Hedging Instrument [Member] | Regulated Distribution Segment [Member]    
Derivatives Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset 0us-gaap_DerivativeFairValueOfDerivativeAsset
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34,477us-gaap_DerivativeFairValueOfDerivativeAsset
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Designated As Hedging Instrument [Member] | Regulated Distribution Segment [Member] | Other Current Assets [Member] | Interest Rate Contract [Member]    
Derivatives Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset   21,869us-gaap_DerivativeFairValueOfDerivativeAsset
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Designated As Hedging Instrument [Member] | Regulated Distribution Segment [Member] | Other Current Assets [Member] | Commodity Contract [Member]    
Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Derivatives Fair Value [Line Items]    
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Nondesignated [Member] | Regulated Distribution Segment [Member] | Deferred Charges And Other Assets [Member] | Commodity Contract [Member]    
Derivatives Fair Value [Line Items]    
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Nondesignated [Member] | Regulated Distribution Segment [Member] | Other Current Liabilities [Member] | Commodity Contract [Member]    
Derivatives Fair Value [Line Items]    
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/ us-gaap_StatementBusinessSegmentsAxis
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(1,730)us-gaap_DerivativeFairValueOfDerivativeLiability
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/ us-gaap_DerivativeInstrumentRiskAxis
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/ us-gaap_HedgingDesignationAxis
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/ us-gaap_StatementBusinessSegmentsAxis
= ato_RegulatedDistributionSegmentMember
Nondesignated [Member] | Regulated Distribution Segment [Member] | Deferred Credits And Other Liabilities [Member] | Commodity Contract [Member]    
Derivatives Fair Value [Line Items]    
Derivative Liability, Fair Value, Gross Liability (1,402)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
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/ us-gaap_DerivativeInstrumentRiskAxis
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/ us-gaap_HedgingDesignationAxis
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/ us-gaap_StatementBusinessSegmentsAxis
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(291)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
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/ us-gaap_HedgingDesignationAxis
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/ us-gaap_StatementBusinessSegmentsAxis
= ato_RegulatedDistributionSegmentMember
Nondesignated [Member] | Nonregulated Segment [Member]    
Derivatives Fair Value [Line Items]    
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/ us-gaap_HedgingDesignationAxis
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/ us-gaap_HedgingDesignationAxis
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/ us-gaap_StatementBusinessSegmentsAxis
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(62,515)us-gaap_DerivativeFairValueOfDerivativeLiability
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/ us-gaap_StatementBusinessSegmentsAxis
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Nondesignated [Member] | Nonregulated Segment [Member] | Other Current Assets [Member] | Commodity Contract [Member]    
Derivatives Fair Value [Line Items]    
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/ us-gaap_StatementBusinessSegmentsAxis
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Nondesignated [Member] | Nonregulated Segment [Member] | Deferred Charges And Other Assets [Member] | Commodity Contract [Member]    
Derivatives Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset 9,036us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_BalanceSheetLocationAxis
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/ us-gaap_DerivativeInstrumentRiskAxis
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/ us-gaap_StatementBusinessSegmentsAxis
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Nondesignated [Member] | Nonregulated Segment [Member] | Other Current Liabilities [Member] | Commodity Contract [Member]    
Derivatives Fair Value [Line Items]    
Derivative Liability, Fair Value, Gross Liability (175,804)us-gaap_DerivativeFairValueOfDerivativeLiability
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/ us-gaap_DerivativeInstrumentRiskAxis
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/ us-gaap_HedgingDesignationAxis
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/ us-gaap_StatementBusinessSegmentsAxis
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(47,729)us-gaap_DerivativeFairValueOfDerivativeLiability
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Nondesignated [Member] | Nonregulated Segment [Member] | Deferred Credits And Other Liabilities [Member] | Commodity Contract [Member]    
Derivatives Fair Value [Line Items]    
Derivative Liability, Fair Value, Gross Liability $ (6,759)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
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/ us-gaap_DerivativeInstrumentRiskAxis
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/ us-gaap_HedgingDesignationAxis
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$ (14,786)us-gaap_DerivativeFairValueOfDerivativeLiability
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