XML 30 R75.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Commitments, Guarantees and Contingencies - Environmental Matters (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2015
Boswell Unit 4 [Member] |
Environmental Matters [Line Items] |
Estimated Capital Expenditures | $ 260 ale_EstimatedCapitalExpendituresIncludingPastExpenditures / ale_GeneratingFacilityAxisAxis = ale_BoswellUnit4Member
Capital Cost Spent to Date | 162 ale_CapitalCostSpentToDate / ale_GeneratingFacilityAxisAxis = ale_BoswellUnit4Member
Maximum [Member] | Clean Water Act - Aquatic Organisms [Member] |
Environmental Matters [Line Items] |
Estimated Environmental Compliance Costs | 15 us-gaap_SiteContingencyLossExposureNotAccruedBestEstimate / us-gaap_EnvironmentalRemediationContingencyAxis = ale_CleanWaterActAquaticOrganismsMember / us-gaap_RangeAxis = us-gaap_MaximumMember
Maximum [Member] | Coal Combustion Residuals [Member] |
Environmental Matters [Line Items] |
Estimated Environmental Compliance Costs | 130 us-gaap_SiteContingencyLossExposureNotAccruedBestEstimate / us-gaap_EnvironmentalRemediationContingencyAxis = ale_CoalCombustionResidualsMember / us-gaap_RangeAxis = us-gaap_MaximumMember
NOV Consent Decree [Member] |
Environmental Matters [Line Items] |
Generating Unit Capacity (MW) | 200.0 ale_GeneratingCapacityMw / ale_EnvironmentalConsentDecreeAxis = ale_NOVConsentDecreeMember
NOV Consent Decree [Member] | Minimum [Member] |
Environmental Matters [Line Items] |
Estimated Capital Expenditures | 20 ale_EstimatedCapitalExpenditures / ale_EnvironmentalConsentDecreeAxis = ale_NOVConsentDecreeMember / us-gaap_RangeAxis = us-gaap_MinimumMember
NOV Consent Decree [Member] | Maximum [Member] |
Environmental Matters [Line Items] |
Estimated Capital Expenditures | $ 40 ale_EstimatedCapitalExpenditures / ale_EnvironmentalConsentDecreeAxis = ale_NOVConsentDecreeMember / us-gaap_RangeAxis = us-gaap_MaximumMember

X
- Definition Capital cost spent to date for project. + References No definition available. + Details
Name: | ale_CapitalCostSpentToDate
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | ale_EnvironmentalMattersLineItems
Namespace Prefix: | ale_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The estimated amount of certain future capital expenditures related to environmental compliance, regulatory matters, or other committments and/or contingencies. + References No definition available. + Details
Name: | ale_EstimatedCapitalExpenditures
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The estimated amount of certain capital expenditures related to environmental compliance, regulatory matters, or other commitments and/or contingencies. This estimate includes expenditures expected in future periods and expenditures made through the end of the current period. + References No definition available. + Details
Name: | ale_EstimatedCapitalExpendituresIncludingPastExpenditures
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 Best estimate of the loss exposure for reasonably possible environmental contingencies at an individual site for which no accrual has been recorded. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 10 -Subparagraph (c),(d)(2) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859 + Details
Name: | us-gaap_SiteContingencyLossExposureNotAccruedBestEstimate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | ale_EnvironmentalConsentDecreeAxis=ale_NOVConsentDecreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GeneratingFacilityAxisAxis=ale_BoswellUnit4Member
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: |