XML 105 R85.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Commitments, Guarantees and Contingencies - Power Purchase Agreements (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2015 USD ($) MWh Years MW | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Square Butte PPA (expires 2026) [Member] | Square Butte Coal-fired Unit [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Entitlement | 50.00% |  |
Square Butte [Member] | Square Butte PPA (expires 2026) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
PPA Counterparty Debt Outstanding | $ | $ 376.4 |  |
PPA Counterparty Annual Debt Service | $ | 45.0 |  |
Cost of Purchased Power | $ | 77.8 | $ 70.1 | $ 71.1
Pro Rata Share of PPA Counterparty Interest Expense | $ | $ 10.1 | $ 10.5 | $ 10.5
Square Butte [Member] | Square Butte PPA (expires 2026) [Member] | Square Butte Coal-fired Unit [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Generating Unit Capacity (MW) | 455 |  |
Minnkota Power [Member] | Square Butte PPA (expires 2026) [Member] | Minnkota Sales Agreement [Member] | Square Butte Coal-fired Unit [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Entitlement | 28.00% | 23.00% |
Minnkota Power [Member] | Minnkota Power PPA (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 50 |  |
NextEra Energy, Inc. [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Number of PPAs | 2 |  |
NextEra Energy, Inc. [Member] | Oliver Wind I PPA (expires 2031) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 50 |  |
Fixed Capacity Charges | $ | $ 0.0 |  |
NextEra Energy, Inc. [Member] | Oliver Wind II PPA (expires 2032) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 48 |  |
Fixed Capacity Charges | $ | $ 0.0 |  |
Manitoba Hydro [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Number of PPAs | 5 |  |
Manitoba Hydro [Member] | Manitoba Hydro PPA (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 50 |  |
Manitoba Hydro [Member] | Manitoba Hydro PPA (expires April 2022) [Member] | Minimum [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MWh) | MWh | 1,000,000 |  |
Manitoba Hydro [Member] | Manitoba Hydro PPA (expires 2035) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 250 |  |
Term of Contract (Years) | Years | 15 |  |
Manitoba Hydro [Member] | Manitoba Hydro PPA (expires 2040) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 133 |  |
Term of Contract (Years) | Years | 20 |  |
Manitoba Hydro [Member] | Manitoba Hydro PPA Beginning June 2017 (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 50 |  |
Great River Energy [Member] | Great River Energy Capacity and Energy PPA (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 50 |  |
Great River Energy [Member] | Great River Energy Capacity Only PPA Beginning June 2016 (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 50 |  |
Great River Energy [Member] | Great River Energy Capacity Only PPA Beginning June 2017 (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 50 |  |
TransAlta [Member] | TransAlta Off-Peak Hours PPA (expires December 2019) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 50 |  |
TransAlta [Member] | TransAlta On-Peak Hours PPA (expire December 2019) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) | 100 |  |
Basin [Member] | Basin Power Sales Agreement (expires April 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Sold (MW) | 100 |  |
Term of Contract (Years) | Years | 10 |  |
Basin [Member] | Basin Power Sales Agreement (expires 2018) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Sold (MW) | 100 |  |
Term of Contract (Years) | Years | 2 |  |

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 Long-Term Contract for Purchase of Electric Power, Fixed Capacity Carges + References No definition available. + Details
Name: | ale_LongTermContractForPurchaseOfElectricPowerFixedCapacityCarges
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Share of plant output being purchased in megawatts under a long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization. + References No definition available. + Details
Name: | ale_LongTermContractForPurchaseOfElectricPowerShareOfPlantOutputBeingPurchasedMw
Namespace Prefix: | ale_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share of plant output being purchased in megawatthours under a long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization. + References No definition available. + Details
Name: | ale_LongTermContractForPurchaseOfElectricPowerShareOfPlantOutputBeingPurchasedMwh
Namespace Prefix: | ale_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Term in years of long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization. + References No definition available. + Details
Name: | ale_LongTermContractForPurchaseOfElectricPowerTermOfContractYears
Namespace Prefix: | ale_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share of plant output being purchased in megawatts under a long-term contract to sell electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization. + References No definition available. + Details
Name: | ale_LongtermContractforSaleofElectricPowerShareofPlantOutputBeingSoldMW
Namespace Prefix: | ale_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Term in years of long-term contract to sell electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization. + References No definition available. + Details
Name: | ale_LongtermContractforSaleofElectricPowerTermofContractYears
Namespace Prefix: | ale_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Long-term Contracts for Electric Power + References No definition available. + Details
Name: | ale_NumberofLongtermContractsforElectricPower
Namespace Prefix: | ale_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Under long-term contracts with public utility districts, cooperatives or other organizations, a utility company receives a portion of the output of a production plant constructed and financed by the district or cooperative. The utility has only a nominal or no investment at all in the plant but pays a proportionate part of the plant's costs, including debt service. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.D) -URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section D + Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAmountOfLongTermDebtOrLeaseObligationOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Under long-term contracts with public utility districts, cooperatives or other organizations, a utility company receives a portion of the output of a production plant constructed and financed by the district or cooperative. The utility has only a nominal or no investment at all in the plant but pays a proportionate part of the plant's costs, including debt service. If the utility is obligated to pay certain minimum amounts which cover debt service requirements whether or not the plant is operating, the amount can be disclosed here. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.D) -URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section D + Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAnnualMinimumDebtServicePaymentRequired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The allocable portion of interest included in charges under a long-term contract to purchase electric power. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.D) -URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section D + Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerInterestIncludedInContractCharges
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_LongTermContractForPurchaseOfElectricPowerLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share of plant output being purchased under a long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.D) -URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section D + Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerShareOfPlantOutputBeingPurchased
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of operating expense for purchased power procured under arrangements extending beyond one year or the normal operating cycle, if longer, by regulated operation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.D) -URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030 + Details
Name: | us-gaap_UtilitiesOperatingExpensePurchasedPowerUnderLongTermContracts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_SquareButtePpaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_CounterpartyNameAxis=ale_SquareButteMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=ale_MinnkotaPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_MinnkotaPpaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=ale_NextEraEnergyInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_OliverWindIPpaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_OliverWindIiPpaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=ale_ManitobaHydroMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_ManitobaHydroPPAexpiresMay2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_ManitobaHydroPpaExpiresApril2022Member
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_LongTermContractForPurchaseOfElectricPowerAxis=ale_ManitobaHydroPpaExpires2035Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_ManitobaHydroPPAexpires2040Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_ManitobaHydroPPABeginningJune2017expiresMay2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=ale_GreatRiverEnergyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_GreatRiverEnergyPPAexpires2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_GreatRiverEnergyCapacityOnlyPPABeginning2016expires2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_GreatRiverEnergyCapacityOnlyPPABeginning2017expires2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=ale_TransAltaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_TransAltaOffPeakHoursPPAexpires2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_TransAltaOnPeakHoursPPAexpire2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=ale_BasinMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_LongtermContractsforSaleofElectricPowerAxis=ale_BasinPowerSalesAgreementexpiresApril2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_LongtermContractsforSaleofElectricPowerAxis=ale_BasinPowerSalesAgreementexpires2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |