XML 47 R33.htm IDEA: XBRL DOCUMENT
v3.8.0.1

REGULATORY MATTERS - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Sep. 30, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | $ 716.6 | $ 791.1 | $ 786.4
Total Regulatory Assets | 865.9 | 966.6 | 920.9
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 335.1 | 157.2 | 132.1
Total Regulatory Liabilities | 356.6 | 179.8 | 176.3
Rate Stabilization and Equalization (RSE) adjustment |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 1.0 | 1.4 | 3.8
Unbilled service margin |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 0.0 | 0.0 | 22.0
Pension and postretirement benefit costs |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 31.5 | 32.2 | 28.3
Refundable negative salvage |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 7.9 | 8.2 | 9.0
Regulatory Liabilities: Non-current | 3.8 | 4.1 | 8.9
Unamortized purchased gas adjustments |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 1.0 | 1.0 | 1.4
Other |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 11.6 | 12.0 | 8.0
Regulatory Liabilities: Non-current | 40.7 | 37.1 | 20.2
Deferred taxes due to customers |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 177.4 | 0.0 | 0.0
Accrued cost of removal |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 81.7 | 83.8 | 74.7
Total Regulatory Liabilities (current) |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 21.5 | 22.6 | 44.2
Total Regulatory Liabilities (non-current) |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 335.1 | 157.2 | 132.1
Pension and postretirement benefit costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 43.0 | 42.2 | 63.2
Regulatory Assets: Non-current | 394.8 | 404.7 | 439.2
Unamortized purchased gas adjustments |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 77.9 | 102.6 | 52.2
Regulatory Assets: Non-current | 0.0 | 9.9 | 4.7
Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 28.4 | 30.7 | 19.1
Regulatory Assets: Non-current | 54.8 | 53.7 | 29.4
Total Current Regulatory Assets |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 149.3 | 175.5 | 134.5
Future income taxes due from customers |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 113.1 | 170.5 | 155.5
Accrued cost of removal |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 123.9 | 123.3 | 131.6
Energy efficiency |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 30.0 | 29.0 | 26.0
Total Noncurrent Regulatory Assets |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 716.6 | 791.1 | 786.4
Spire Missouri |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 484.1 | 557.8 | 543.4
Total Regulatory Assets | 560.8 | 653.4 | 636.9
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 241.2 | 81.2 | 67.3
Total Regulatory Liabilities | 243.9 | 83.9 | 70.0
Spire Missouri | Other |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 2.7 | 2.7 | 2.7
Regulatory Liabilities: Non-current | 30.0 | 26.7 | 12.5
Spire Missouri | Deferred taxes due to customers |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 159.2 | 0.0 | 0.0
Spire Missouri | Accrued cost of removal |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 52.0 | 54.5 | 54.8
Spire Missouri | Total Regulatory Liabilities (current) |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 2.7 | 2.7 | 2.7
Spire Missouri | Total Regulatory Liabilities (non-current) |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 241.2 | 81.2 | 67.3
Spire Missouri | Pension and postretirement benefit costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 34.9 | 34.9 | 56.3
Regulatory Assets: Non-current | 315.8 | 322.7 | 333.3
Spire Missouri | Unamortized purchased gas adjustments |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 38.5 | 57.4 | 33.8
Regulatory Assets: Non-current | 0.0 | 9.9 | 4.7
Spire Missouri | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 3.3 | 3.3 | 3.4
Regulatory Assets: Non-current | 25.2 | 25.7 | 23.9
Spire Missouri | Total Current Regulatory Assets |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 76.7 | 95.6 | 93.5
Spire Missouri | Future income taxes due from customers |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 113.1 | 170.5 | 155.5
Spire Missouri | Energy efficiency |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 30.0 | 29.0 | 26.0
Spire Missouri | Total Noncurrent Regulatory Assets |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 484.1 | 557.8 | 543.4
Spire Alabama |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 197.4 | 197.0 | 229.5
Total Regulatory Assets | 255.4 | 261.6 | 261.0
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 39.0 | 39.6 | 40.6
Total Regulatory Liabilities | 50.3 | 51.6 | 78.0
Spire Alabama | Rate Stabilization and Equalization (RSE) adjustment |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 1.0 | 1.4 | 3.8
Spire Alabama | Unbilled service margin |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 0.0 | 0.0 | 22.0
Spire Alabama | Pension and postretirement benefit costs |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 31.5 | 32.2 | 28.3
Spire Alabama | Refundable negative salvage |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 7.9 | 8.2 | 9.0
Regulatory Liabilities: Non-current | 3.9 | 4.1 | 8.9
Spire Alabama | Other |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 2.4 | 2.4 | 2.6
Regulatory Liabilities: Non-current | 3.6 | 3.3 | 3.4
Spire Alabama | Total Regulatory Liabilities (current) |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Current | 11.3 | 12.0 | 37.4
Spire Alabama | Total Regulatory Liabilities (non-current) |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liabilities: Non-current | 39.0 | 39.6 | 40.6
Spire Alabama | Pension and postretirement benefit costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 7.2 | 7.2 | 6.8
Regulatory Assets: Non-current | 70.8 | 72.6 | 96.8
Spire Alabama | Unamortized purchased gas adjustments |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 39.4 | 45.2 | 17.1
Spire Alabama | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 11.4 | 12.2 | 7.6
Regulatory Assets: Non-current | 2.7 | 1.1 | 1.1
Spire Alabama | Total Current Regulatory Assets |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Current | 58.0 | 64.6 | 31.5
Spire Alabama | Accrued cost of removal |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | 123.9 | 123.3 | 131.6
Spire Alabama | Total Noncurrent Regulatory Assets |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets: Non-current | $ 197.4 | $ 197.0 | $ 229.5

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_RegulatoryAssetLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
Name: | us-gaap_RegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
Name: | us-gaap_RegulatoryAssetsCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
Name: | us-gaap_RegulatoryAssetsNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
Name: | us-gaap_RegulatoryLiabilities
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_RegulatoryLiabilitiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
Name: | us-gaap_RegulatoryLiabilityCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period. + 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 210.5-02.24) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_RegulatoryLiabilityNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=lg_RSEAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=lg_UnbilledServiceMarginMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=lg_PensionandPostretirementBenefitCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_RevenueSubjectToRefundMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=lg_UnamortizedPurchasedGasAdjustmentsLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=lg_OtherRegulatoryLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=lg_EstimatedDeferredTaxesduetocustomersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_RemovalCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=lg_RegulatoryLiabilityCurrentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=lg_RegulatoryLiabilityNoncurrentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=lg_PensionandPostretirementBenefitCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=lg_UnamortizedPurchasedGasAdjustmentsAssetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_OtherRegulatoryAssetsLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=lg_RegulatoryAssetsCurrentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_DeferredIncomeTaxChargesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_RemovalCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_RenewableEnergyProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=lg_RegulatoryAssetsNoncurrentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lg_SpireMissouriMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lg_SpireAlabamaIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |