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Plan Asset Allocations (Details) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2011 | Dec. 31, 2010
Plan Asset Target Allocations [Abstract] |  |  |  |
ALLETE Common Stock Included in Pension Plan Equity Securities | 20,000,000 |  | 0 |
Stock Issued During Period, Shares, Employee Benefit Plan | 507,600 |  |  |
Pension [Member] |  |  |  |
Plan Asset Target Allocations [Abstract] |  |  |  |
Equity Securities Target Allocation | 52.00% |  |  |
Debt Securities Target Allocation | 30.00% |  |  |
Real Estate Target Allocation | 9.00% |  |  |
Private Equity Target Allocation | 9.00% |  |  |
Pension [Member] | Equity Securities [Member] |  |  |  |
Actual Plan Asset Allocations [Abstract] |  |  |  |
Actual Plan Asset Allocation | 52.00% |  | 52.00% |
Pension [Member] | Debt Securities [Member] |  |  |  |
Actual Plan Asset Allocations [Abstract] |  |  |  |
Actual Plan Asset Allocation | 27.00% |  | 29.00% |
Pension [Member] | Real Estate [Member] |  |  |  |
Actual Plan Asset Allocations [Abstract] |  |  |  |
Actual Plan Asset Allocation | 5.00% |  | 5.00% |
Pension [Member] | Private Equity [Member] |  |  |  |
Actual Plan Asset Allocations [Abstract] |  |  |  |
Actual Plan Asset Allocation | 16.00% |  | 14.00% |
Postretirement Health and Life [Member] |  |  |  |
Plan Asset Target Allocations [Abstract] |  |  |  |
Equity Securities Target Allocation | 48.00% | [1] |  |
Debt Securities Target Allocation | 34.00% | [1] |  |
Real Estate Target Allocation | 9.00% | [1] |  |
Private Equity Target Allocation | 9.00% | [1] |  |
Postretirement Health and Life [Member] | Equity Securities [Member] |  |  |  |
Actual Plan Asset Allocations [Abstract] |  |  |  |
Actual Plan Asset Allocation | 51.00% | [1] | 58.00% | [1]
Postretirement Health and Life [Member] | Debt Securities [Member] |  |  |  |
Actual Plan Asset Allocations [Abstract] |  |  |  |
Actual Plan Asset Allocation | 39.00% | [1] | 33.00% | [1]
Postretirement Health and Life [Member] | Real Estate [Member] |  |  |  |
Actual Plan Asset Allocations [Abstract] |  |  |  |
Actual Plan Asset Allocation | 0.00% | [1] | 0.00% | [1]
Postretirement Health and Life [Member] | Private Equity [Member] |  |  |  |
Actual Plan Asset Allocations [Abstract] |  |  |  |
Actual Plan Asset Allocation | 10.00% | [1] | 9.00% | [1]
[1] | (a)Includes VEBAs and irrevocable grantor trusts.

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- Definition The number of employer shares or related party shares included in plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph n -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 -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (n) -URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920 + Details
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- Definition Target allocation percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph d(2) -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 -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c)(i) -URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e2446-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920 + Details
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- Definition Target allocation percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position. + References No definition available. + Details
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- Definition Target allocation percentage in other than debt securities, equity securities, and real estate to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position. + References No definition available. + Details
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- Definition Target allocation percentage of investments in real estate to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position. + References No definition available. + Details
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- Definition The aggregate percentage of the fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of total plan assets held as of the measurement date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph d(1) -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 -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e2446-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920 + Details
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- Definition Number of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan. + References No definition available. + Details
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