XML 47 R36.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Debt (Details) - USD ($) | 3 Months Ended
--- | ---
Mar. 31, 2018 | Sep. 30, 2017
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 3,085,000,000 | $ 3,085,000,000
Debt Instrument, Unamortized Discount (Premium), Net |  | (4,412,000) | (4,384,000)
Debt Issuance Costs, Net |  | 21,520,000 | 22,339,000
Current maturities of long-term debt |  | 450,000,000 | 0
Long-term debt |  | 2,617,892,000 | 3,067,045,000
Line Of Credit Facility [Line Items] |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  | 1,500,000,000 |
Long Term Debt Other Disclosures [Abstract] |  |  |
Term Loan Agreement, Maximum Borrowing Capacity |  | 200,000,000 | 200,000,000
Commercial Paper |  | $ 129,600,000 | 447,700,000
Required by Covenant [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Ratio of Total Debt to Total Capital |  | 70.00% |
Actual [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Ratio of Total Debt to Total Capital |  | 41.00% |
Minimum [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Equity to Capitalization Ratio |  | 50.00% |
Minimum [Member] | Required by Covenant [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Excess of Debt |  | $ 15,000,000 |
Maximum [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Equity to Capitalization Ratio |  | 60.00% |
Maximum [Member] | Required by Covenant [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Excess of Debt |  | $ 100,000,000 |
Five Year Unsecured Revolving Credit Agreement [Member] | Commercial Paper [Member] | Regulated Operation [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  | 1,500,000,000.0 |
Line of Credit Facility, Accordion Feature |  | 250,000,000 |
Line of Credit Facility, Maximum Borrowing Capacity with Accordion Feature |  | $ 1,750,000,000.00 |
Five Year Unsecured Revolving Credit Agreement [Member] | Commercial Paper [Member] | Minimum [Member] | Regulated Operation [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 0.00% |
Five Year Unsecured Revolving Credit Agreement [Member] | Commercial Paper [Member] | Maximum [Member] | Regulated Operation [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 1.25% |
$25 Million Bank Loan Agreement [Member] | Unsecured Loan Agreement [Member] | Regulated Operation [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  | $ 25,000,000 |
Line of Credit Facility, Fair Value of Amount Outstanding |  | 0 |
$10 Million Revolving Credit Note [Member] | Unsecured Revolving Credit Note [Member] | Regulated Operation [Member] |  |  |
Line Of Credit Facility [Line Items] |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  | 10,000,000 |
Line of Credit Facility, Remaining Borrowing Capacity |  | 4,400,000 |
Line of Credit Facility, Fair Value of Amount Outstanding |  | 0 |
Unsecured Senior Notes Due 2019 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 450,000,000 | $ 450,000,000
Debt Instrument, Interest Rate, Stated Percentage |  | 8.50% | 8.50%
Debt Instrument, Maturity Date |  | Mar. 15, 2019 | Mar. 15, 2019
Unsecured Senior Notes Due 2027 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 500,000,000 | $ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage |  | 3.00% | 3.00%
Debt Instrument, Maturity Date |  | Jun. 15, 2027 | Jun. 15, 2027
Unsecured Senior Notes Due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 200,000,000 | $ 200,000,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.95% | 5.95%
Debt Instrument, Maturity Date |  | Oct. 15, 2034 | Oct. 15, 2034
Unsecured Senior Notes Due 2041 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 400,000,000 | $ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.50% | 5.50%
Debt Instrument, Maturity Date |  | Jun. 15, 2041 | Jun. 15, 2041
Unsecured Senior Notes Due 2043 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 500,000,000 | $ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage |  | 4.15% | 4.15%
Debt Instrument, Maturity Date |  | Jan. 15, 2043 | Jan. 15, 2043
Unsecured Senior Notes Due 2044 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 750,000,000 | $ 750,000,000
Debt Instrument, Interest Rate, Stated Percentage |  | 4.125% | 4.125%
Debt Instrument, Maturity Date |  | Oct. 15, 2044 | Oct. 15, 2044
Medium Term Notes Due 2025 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 10,000,000 | $ 10,000,000
Debt Instrument, Interest Rate, Stated Percentage |  | 6.67% | 6.67%
Debt Instrument, Maturity Date |  | Dec. 15, 2025 | Dec. 15, 2025
Unsecured Debentures Due 2028 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount |  | $ 150,000,000 | $ 150,000,000
Debt Instrument, Interest Rate, Stated Percentage |  | 6.75% | 6.75%
Debt Instrument, Maturity Date |  | Jul. 15, 2028 | Jul. 15, 2028
Multi-Draw Term Loan Due 2019 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument Carrying Amount | [1] | $ 125,000,000 | $ 125,000,000
Debt Instrument, Maturity Date |  | Sep. 22, 2019 | Sep. 22, 2019
[1] | Up to $200 million can be drawn under this term loan.

X
- Definition Equity to Capitalization Ratio + References No definition available. + Details
Name: | ato_EquitytoCapitalizationRatio
Namespace Prefix: | ato_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total outstanding indebtedness arising out of any other credit agreements, as stated in the public debt indentures relating to senior notes and debentures, as well as certain revolving credit agreements. + References No definition available. + Details
Name: | ato_ExcessofDebt
Namespace Prefix: | ato_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum available borrowing capacity under the credit facility with consideration of any additional commited line portions under the accordion feature that could be borrowed against with the approval of the issuing banks. + References No definition available. + Details
Name: | ato_LineOfCreditFacilityMaximumBorrowingCapacityWithAccordionFeature
Namespace Prefix: | ato_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Monetary value of the accordion feature, the additional line of credit portion that could be borrowed against with the approval of the issuing banks. + References No definition available. + Details
Name: | ato_LineofCreditFacilityAccordionFeature
Namespace Prefix: | ato_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition For covenant purposes, total debt divided by total capitalization including original issue discount, short-term debt, capital leases, operating leases and guaranty obligations. + References No definition available. + Details
Name: | ato_RatioofTotalDebttoTotalCapital
Namespace Prefix: | ato_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The maximum borrowing capacity under a multi-draw term loan agreement. + References No definition available. + Details
Name: | ato_TermLoanAgreementMaximumBorrowingCapacity
Namespace Prefix: | ato_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(19)(a)(3)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(13)(2)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_CommercialPaper
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentMaturityDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after accumulated amortization, of debt discount (premium). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28567-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399 + Details
Name: | us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DeferredFinanceCostsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of the amount outstanding under the credit facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13476-108611 + Details
Name: | us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_LongTermDebtOtherDisclosuresAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | ato_CovenantComplianceAxis=ato_RequiredbyCovenantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ato_CovenantComplianceAxis=ato_ActualMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LineOfCreditFacilityAxis=ato_FiveYearUnsecuredRevolvingCreditAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditFacilityAxis=us-gaap_CommercialPaperMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis=us-gaap_RegulatedOperationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LineOfCreditFacilityAxis=ato_A25MillionBankLoanAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditFacilityAxis=ato_UnsecuredLoanAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LineOfCreditFacilityAxis=ato_A10MillionRevolvingCreditNoteMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditFacilityAxis=ato_UnsecuredRevolvingCreditNoteMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_UnsecuredSeniorNotesDue2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_UnsecuredSeniorNotesDue2027Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_UnsecuredSeniorNotesDue2034Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_UnsecuredSeniorNotesDue2041Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_UnsecuredSeniorNotesDue2043Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_UnsecuredSeniorNotesDue2044Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_MediumTermNotesDue2025Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_UnsecuredDebenturesDue2028Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ato_MultiDrawTermLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |