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Regulatory Matters - Great Northern Transmission Line (GNTL) (Details) (Great Northern Transmission Line [Member]) | Mar. 31, 2015 kV Miles
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Great Northern Transmission Line [Member] |
Transmission [Line Items] |
Transmission Line Length (Miles) | 220 ale_TransmissionLineLengthMiles / ale_TransmissionAxis = ale_GreatNorthernTransmissionLineMember
Transmission Line Capacity (kV) | 500 ale_TransmissionLineCapacityKv / ale_TransmissionAxis = ale_GreatNorthernTransmissionLineMember

X
- Definition Capacity of a transmission line in kilovolts. + References No definition available. + Details
Name: | ale_TransmissionLineCapacityKv
Namespace Prefix: | ale_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Length of a transmission line in miles. + References No definition available. + Details
Name: | ale_TransmissionLineLengthMiles
Namespace Prefix: | ale_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant