XML 121 R101.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Pension and Other Postretirement Benefit Plans - Contributions (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plans, Employer Contributions | $ 0.0 | $ 0.0 | $ 10.8
Defined Benefit Plans, Employer Contributions | 0.0 | 19.5 | 0.0
Defined Contribution RSOP, Employer Contributions | 9.0 | 9.1 | 8.4
Pension Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plans, Employer Contributions | 0.0 | 0.0 | 0.0
Defined Benefit Plans, Employer Contributions |  | 19.5 |
Defined Benefit Plans, Expected Employer Contributions in 2016 | 2.0 |  |
Postretirement Health and Life [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plans, Expected Employer Contributions in 2016 | 0.0 |  |
VEBA [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plans, Employer Contributions | 0.0 | 0.0 | 10.8
Irrevocable Grantor Trust [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefit Plans, Employer Contributions | $ 0.0 | $ 0.0 | $ 2.0

X
- Definition Amount employer contributed during the period, to match employee contributions, to a defined contribution plan. Includes, but not limited to, contributions made through Employee Stock Ownership Plans (ESOP). + References No definition available. + Details
Name: | ale_DefinedContributionPlanEmployerMatchingContributionAmount
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of cash or cash equivalents contributed during the reporting period by the entity to fund its pension plans and its non-pension postretirement benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3536-108585 + Details
Name: | us-gaap_PensionAndOtherPostretirementBenefitContributions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Value of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan. + References No definition available. + Details
Name: | us-gaap_StockIssuedDuringPeriodValueEmployeeBenefitPlan
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=ale_VebaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_TrustForBenefitOfEmployeesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |