XML 56 R62.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Acquisitions - ACE Agreement (Details) (ACE Agreement [Member], USD $) In Millions, unless otherwise specified | 0 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2014 MW
ACE Agreement [Member] |  |
Business Acquisition [Line Items] |  |
Member's Interest Purchase Agreement | $ 47.5 ale_MembersInterestPurchaseAgreement / us-gaap_BusinessAcquisitionAxis = ale_ACEAgreementMember |
Generating Capacity (MW) | 97.5 ale_GeneratingCapacityMw / us-gaap_BusinessAcquisitionAxis = ale_ACEAgreementMember | 97.5 ale_GeneratingCapacityMw / us-gaap_BusinessAcquisitionAxis = ale_ACEAgreementMember

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 Member's Interest Purchase Agreement + References No definition available. + Details
Name: | ale_MembersInterestPurchaseAgreement
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration