XML 82 R63.htm IDEA: XBRL DOCUMENT
v3.2.0.727

Regulatory Matters - MISO Return on Equity Complaints (Details) - Jun. 30, 2015 - USD ($) $ in Millions | Total
--- | ---
Loss Contingencies [Line Items] |
Estimated Refund Obligation | $ 5.6
Estimated Refund | $ 3.7
FERC Complaint 1 [Member] |
Loss Contingencies [Line Items] |
Equity Method Investment, Proposed Return on Common Equity | 9.15%
FERC Complaint 2 [Member] |
Loss Contingencies [Line Items] |
Equity Method Investment, Proposed Return on Common Equity | 8.67%
Minnesota Power [Member] |
Loss Contingencies [Line Items] |
Loss Contingency, Estimate of Possible Loss | $ 1.9
Minnesota Power [Member] | FERC Complaint 2 [Member] |
Loss Contingencies [Line Items] |
Loss Contingency, Estimate of Possible Loss | $ 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 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 Reflects the estimated amount of loss from the specified contingency as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyEstimateOfPossibleLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Details
Name: | ale_FERCComplaintAxis=ale_FERCComplaint2Member
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: |