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v2.4.1.9

Short-Term and Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified | 9 Months Ended | 0 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2014 | Mar. 04, 2014 | Jun. 26, 2014 | Sep. 16, 2014 | Dec. 31, 2014 | Jan. 30, 2014 | Dec. 31, 2013
Debt Instrument [Line Items] |  |  |  |  |  |  |
Short-Term Debt |  |  |  |  | $ 104.4 us-gaap_DebtCurrent |  | $ 27.2 us-gaap_DebtCurrent
Lines of Credit, Current |  |  |  |  | 47.5 us-gaap_LinesOfCreditCurrent |  | 5.4 us-gaap_LinesOfCreditCurrent
Letters of Credit Drawn |  |  |  |  | 3.7 ale_LettersofCreditDrawn |  | 0 ale_LettersofCreditDrawn
Long-Term Debt |  |  |  |  | 1,272.8 us-gaap_LongTermDebtNoncurrent |  | 1,083.0 us-gaap_LongTermDebtNoncurrent
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Long-term Debt |  |  |  |  |  | 23.3 ale_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLongtermDebt |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-term Debt |  |  |  |  |  | 2.2 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt |
Long-Term Debt Due Within One Year |  |  |  |  | 100.7 us-gaap_LongTermDebtCurrent |  | 27.2 us-gaap_LongTermDebtCurrent
Long-Term Debt, 2016 Maturities |  |  |  |  | 24.9 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo |  |
Long-Term Debt, 2017 Maturities |  |  |  |  | 54.6 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree |  |
Long-Term Debt, 2018 Maturities |  |  |  |  | 54.8 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour |  |
Long-Term Debt, 2019 Maturities |  |  |  |  | 46.9 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive |  |
Long-Term Debt, Thereafter Maturities |  |  |  |  | 1,091.6 us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive |  |
Proceeds from Issuance of First Mortgage Bond | 375.0 us-gaap_ProceedsFromIssuanceOfFirstMortgageBond |  |  |  |  |  |
Lines of Credit [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  |  |  | 408.4 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity / us-gaap_DebtInstrumentAxis = ale_ConsolidatedLinesOfCreditMemberMember |  | 406.4 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity / us-gaap_DebtInstrumentAxis = ale_ConsolidatedLinesOfCreditMemberMember
ALLETE Bonds 3.69% Due March2024 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Issuance of First Mortgage Bond |  | 60.0 us-gaap_ProceedsFromIssuanceOfFirstMortgageBond / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds3.69DueMarch2024Member |  |  |  |  |
First Mortgage Bonds, Interest Rate |  | 3.69%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds3.69DueMarch2024Member |  |  |  |  |
ALLETE Bonds 4.95% Due March2044 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Issuance of First Mortgage Bond |  | 40.0 us-gaap_ProceedsFromIssuanceOfFirstMortgageBond / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds4.95DueMarch2044Member |  |  |  |  |
First Mortgage Bonds, Interest Rate |  | 4.95%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds4.95DueMarch2044Member |  |  |  |  |
ALLETE Bonds 3.40% Due July2022 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Issuance of First Mortgage Bond |  |  | 75.0 us-gaap_ProceedsFromIssuanceOfFirstMortgageBond / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds3.40DueJuly2022Member |  |  |  |
First Mortgage Bonds, Interest Rate |  |  | 3.40%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds3.40DueJuly2022Member |  |  |  |
ALLETE Bonds 5.05% Due July2044 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Issuance of First Mortgage Bond |  |  | 40.0 us-gaap_ProceedsFromIssuanceOfFirstMortgageBond / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds5.05DueJuly2044Member |  |  |  |
First Mortgage Bonds, Interest Rate |  |  | 5.05%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds5.05DueJuly2044Member |  |  |  |
ALLETE Bonds 3.02% Due September 2021 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Issuance of First Mortgage Bond |  |  |  | 60.0 us-gaap_ProceedsFromIssuanceOfFirstMortgageBond / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds3.02DueSeptember2021Member |  |  |
First Mortgage Bonds, Interest Rate |  |  |  | 3.02%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds3.02DueSeptember2021Member |  |  |
ALLETE Bonds 3.74% Due September 2029 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Issuance of First Mortgage Bond |  |  |  | 50.0 us-gaap_ProceedsFromIssuanceOfFirstMortgageBond / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds3.74DueSeptember2029Member |  |  |
First Mortgage Bonds, Interest Rate |  |  |  | 3.74%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds3.74DueSeptember2029Member |  |  |
ALLETE Bonds 4.39% Due September 2044 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Proceeds from Issuance of First Mortgage Bond |  |  |  | $ 50.0 us-gaap_ProceedsFromIssuanceOfFirstMortgageBond / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds4.39DueSeptember2044Member |  |  |
First Mortgage Bonds, Interest Rate |  |  |  | 4.39%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = ale_ALLETEBonds4.39DueSeptember2044Member |  |  |

X
- Definition Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Long-term Debt, Including current portion + References No definition available. + Details
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- Definition Amount of long-term debt due within one year or within the normal operating cycle, if longer, assumed at the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 + Details
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- Definition Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5 + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
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- Definition The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 20 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Line-of-Credit Arrangement -URI http://asc.fasb.org/extlink&oid=6517033 + Details
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- Definition Amount of long-term debt, after unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04.(a)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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- Definition The cash inflow from amounts received from a long-term debt instrument secured by a first mortgage deed of trust, containing a pledge of real property. The lender has the highest claim on the property in case of default. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
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