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Short-Term and Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2012 | Jun. 30, 2012 | Dec. 31, 2011
Short-Term and Long-Term Debt [Abstract] |  |  |
Short-Term Debt Outstanding | $ 67.4 | $ 67.4 | $ 6.5
Short-Term Debt, Amount Expected to be Refinanced |  | 60 |
Debt Instrument [Line Items] |  |  |
Long-Term Debt Outstanding | 808.4 | 808.4 | 857.9
Proceeds from Issuance of First Mortgage Bonds | 160.0 |  |
Required Indebtedness to Total Capital Ratio | 0.65 to 1.00 |  |
Actual Indebtedness to Total Capital Ratio | 0.43 to 1.00 | 0.43 to 1.00 |
ALLETE LOC Jan2014 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Line of Credit, Amount Outstanding | 14.0 | 14.0 |
Line of Credit, Maximum Borrowing Capacity | 150.0 | 150.0 |
ALLETE First Mortgage Bonds 3.20% Due July2026 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Proceeds from Issuance of First Mortgage Bonds | 75.0 |  |
Interest Rate | 3.20% | 3.20% |
ALLETE First Mortgage Bonds 4.08% Due July2042 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Proceeds from Issuance of First Mortgage Bonds | 85.0 |  |
Interest Rate | 4.08% | 4.08% |
Industrial Development Revenue Bonds 6.5% Due 2025 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Interest Rate | 6.50% | 6.50% |
Amount of Redeemed Bonds | $ 6.0 |  |

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- Definition The amount of debt that was reclassified (from long-term) as short-term because it is due w/in one year of the balance sheet date, but that the company intends to refinance prior to maturity. + References No definition available. + Details
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- Definition Carrying value as of the balance sheet date of the sum of short-term debt and current maturities of long-term debt and capital lease obligations, which are due within one year (or one business 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 Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). 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 210.5-02.22) -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 22 -Article 5 + 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 Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: 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=6943989&loc=d3e3255-108585 + Details
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