XML 81 R61.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Regulatory Matters - MISO Return on Equity Complaints (Details) - FERC [Member] $ in Millions | Dec. 31, 2015 USD ($)
--- | ---
Return on Equity Complaint 1 [Member] |
Loss Contingencies [Line Items] |
Proposed Return on Common Equity | 9.15%
Return on Equity Complaint 2 [Member] |
Loss Contingencies [Line Items] |
Proposed Return on Common Equity | 8.67%
Return on Equity Complaints [Member] |
Loss Contingencies [Line Items] |
Proposed Return on Common Equity | 10.32%
Return on Equity Complaints [Member] | Minnesota Power [Member] |
Loss Contingencies [Line Items] |
Estimated Refund Obligation for MISO Revenue | $ 7.2
Estimated Refund for MISO Transmission Expense | 4.5
Reserve | 2.7
Reserve, Portion Attributable to Prior Years | $ 1.5

X
- Definition The proposed return on common equity, which would be dedicated to the utility plant in the investee accounted for under the equity method of accounting. + References No definition available. + Details
Name: | ale_EquityMethodInvestmentProposedReturnonCommonEquity
Namespace Prefix: | ale_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Estimated Refund + References No definition available. + Details
Name: | ale_EstimatedRefund
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Estimated Refund Obligation + References No definition available. + Details
Name: | ale_EstimatedRefundObligation
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of a loss contingency accrual recorded in the current current but attributable to prior years. + References No definition available. + Details
Name: | ale_LossContingencyAccrualAttributabletoPriorYears
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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_LossContingenciesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of loss contingency liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 + Details
Name: | us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=ale_FERCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_FERCComplaint1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_FERCComplaint2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_ReturnonEquityComplaintsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=ale_MinnesotaPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |