XML 65 R52.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Regulatory Matters - Utility Rates (Details) $ in Millions |  |  |  | 9 Months Ended
--- | --- | --- | --- | ---
Nov. 02, 2016 USD ($) | Jun. 28, 2016 USD ($) | Jun. 01, 2011 | Sep. 30, 2016 USD ($) Customers Years MW | Sep. 30, 2015 USD ($)
Minnesota Power [Member] | Bison Wind Energy Center [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Generating Capacity (MW) | MW |  |  |  | 497 |
PSCW [Member] | 2012 Wisconsin Rate Case [Member] | SWL&P [Member] | Retail [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Approved Return on Common Equity |  |  |  | 10.90% |
PSCW [Member] | 2016 Wisconsin Rate Case [Member] | SWL&P [Member] | Retail [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Requested Rate Increase (Decrease) |  | 3.10% |  |  |
Requested Return on Equity |  | 10.90% |  |  |
Requested Equity Capital Structure |  | 55.00% |  |  |
Requested Debt Capital Structure |  | 45.00% |  |  |
Annual Additional Revenue Generated from Overall Requested Rate Increase |  | $ 2.7 |  |  |
Electric Rates [Member] | MPUC [Member] | 2010 Minnesota Rate Case [Member] | Minnesota Power [Member] | Retail [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Approved Return on Common Equity |  |  | 10.38% | 10.38% |
Approved Equity Ratio |  |  |  | 54.29% |
Electric Rates [Member] | MPUC [Member] | Minnesota Cost Recovery Riders [Member] | Minnesota Power [Member] | Retail [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Revenue from Cost Recovery Riders |  |  |  | $ 73.9 | $ 67.8
Electric Rates [Member] | MPUC [Member] | 2016 Minnesota Rate Case [Member] | Minnesota Power [Member] | Retail [Member] | Subsequent Event [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Requested Rate Increase (Decrease) | 9.00% |  |  |  |
Requested Return on Equity | 10.25% |  |  |  |
Requested Equity Capital Structure | 53.80% |  |  |  |
Requested Debt Capital Structure | 46.20% |  |  |  |
Annual Additional Revenue Generated from Overall Requested Rate Increase | $ 55.0 |  |  |  |
Expected Interim Rates | $ 49.0 |  |  |  |
Electric Rates [Member] | MPUC [Member] | Renewable Cost Recovery Rider [Member] | Retail [Member] | Corporate and Other [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
After-Tax Charge for North Dakota Investment Tax Credits Reversed |  |  |  | 8.8 |
Electric Rates [Member] | MPUC [Member] | Renewable Cost Recovery Rider [Member] | Minnesota Power [Member] | Retail [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Reduction in Operating Revenue due to Regulatory Outcome |  |  |  | $ 15.0 |
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Number of Customers | Customers |  |  |  | 16 |
Length of Notice Required to Terminate Contract (Years) | Years |  |  |  | 3 |
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member] | Wholesale Electric Contracts (Expire December 2024) [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Number of Customers | Customers |  |  |  | 14 |
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member] | Wholesale Electric Contracts (Expire December 2024) [Member] | Maximum [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Change in Annual Capacity Charge Per Contract - Percentage |  |  |  | 2.00% |
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member] | Wholesale Electric Contracts (Expire December 2024) [Member] | Minimum [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Change in Annual Capacity Charge Per Contract - Percentage |  |  |  | (1.00%) |
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member] | Wholesale Electric Contract (Termination Effective June 2019) [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Number of Customers | Customers |  |  |  | 1 |
Average Monthly Demand (MW) | MW |  |  |  | 29 |
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member] | Wholesale Electric Contract (Cost-Based Formula Methodology for Entire Term) [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Number of Customers | Customers |  |  |  | 3 |
Electric Rates [Member] | PSCW [Member] | 2016 Wisconsin Rate Case [Member] | SWL&P [Member] | Retail [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Requested Rate Increase (Decrease) |  | 3.50% |  |  |
Natural Gas Rates [Member] | PSCW [Member] | 2016 Wisconsin Rate Case [Member] | SWL&P [Member] | Retail [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Requested Rate Increase (Decrease) |  | (1.30%) |  |  |
Water Rates [Member] | PSCW [Member] | 2016 Wisconsin Rate Case [Member] | SWL&P [Member] | Retail [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Requested Rate Increase (Decrease) |  | 7.80% |  |  |

X
- Definition Average demand measured for a specified customer, measured in MW. + References No definition available. + Details
Name: | ale_AverageCustomerDemandMW
Namespace Prefix: | ale_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The annual percentage change of the capacity charge specified in a power purchase, power sales, or electric sales agreement. + References No definition available. + Details
Name: | ale_ChangeinAnnualCapacityChargePerContractPercentage
Namespace Prefix: | ale_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Capacity of a generating facility, unit, or project in megawatts. + References No definition available. + Details
Name: | ale_GeneratingCapacityMw
Namespace Prefix: | ale_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The length of notice required to terminate a contract (in years). + References No definition available. + Details
Name: | ale_LengthOfNoticeRequiredToTerminateYears
Namespace Prefix: | ale_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Customers + References No definition available. + Details
Name: | ale_NumberOfCustomers
Namespace Prefix: | ale_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of public utility's approved equity to capital, including debt and equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedEquityCapitalStructurePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's approved return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Amount of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesInterimRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's requested debt to capital, including debt and equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedDebtCapitalStructurePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's requested equity to capital, including debt and equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedEquityCapitalStructurePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreasePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's requested return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The total amount of regulated operating revenues recognized during the period. + References No definition available. + Details
Name: | us-gaap_RegulatedOperatingRevenue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of regulated other operating revenues recognized during the period. + References No definition available. + Details
Name: | us-gaap_RegulatedOperatingRevenueOther
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase (decrease) to previously recorded tax expense. Includes, but is not limited to, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, and IRS tax settlement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 25 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=68052875&loc=d3e28446-109314 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 25 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=68052875&loc=d3e28511-109314 + Details
Name: | us-gaap_TaxAdjustmentsSettlementsAndUnusualProvisions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Details
Name: | ale_GeneratingFacilityAxisAxis=ale_BisonWindEnergyCenterMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=ale_PSCWMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_A2012WisconsinRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | ale_CustomerClassAxis=ale_RetailCustomersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_A2016WisconsinRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_RateTypeAxis=ale_ElectricRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=ale_MPUCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_A2010RateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_CurrentCostRecoveryRiderMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_A2016MinnesotaRateCaseMemberMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_RenewableCostRecoveryRiderMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=us-gaap_CorporateAndOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=ale_FERCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_FercApprovedWholesaleRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_CustomerClassAxis=ale_MunicipalCustomersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_LongtermContractsforSaleofElectricPowerAxis=ale_WholesaleElectricContractsExpireDecember2024Member
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_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_LongtermContractsforSaleofElectricPowerAxis=ale_WholesaleElectricContractTerminationEffectiveJune2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_LongtermContractsforSaleofElectricPowerAxis=ale_WholesaleElectricContractCostBasedFormulaMethodologyforEntireTermMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_RateTypeAxis=ale_NaturalGasRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_RateTypeAxis=ale_WaterRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |