ALLETE's Investment in ATC [Roll Forward]

No definition available.

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- Definition

A sensitivity analysis using basis point reduction.

+ References

No definition available.

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The approved percentage return on common equity dedicated to the utility plant in the investee accounted for under the equity method of accounting.

+ References

No definition available.

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- Definition

The approved percentage return on common equity, including an incentive adder for participation in a regional transmission organization dedicated to the utility plant in the investee accounted for under the equity method of accounting.

+ References

No definition available.

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- Definition

Additional investments expected to be made during the current fiscal year but after the filing date, not already separately disclosed as part of current period/year-to-date investments or as a subsequent event.

+ References

No definition available.

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- 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.

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- Definition

The proposed return on common equity, including an incentive adder for participation in a regional transmission organization, which would be dedicated to the utility plant in the investee accounted for under the equity method of accounting.

+ References

No definition available.

+ Details

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- Definition

The quantified amount of the future effect on earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4)
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- Definition

Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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-Name Accounting Standards Codification
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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

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- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

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- 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

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Investment in ATC (Details) $ in Millions		3 Months Ended		9 Months Ended
Investment in ATC (Details) $ in Millions	Oct. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
ALLETE's Investment in ATC [Roll Forward]
Equity Investment Balance as of December 31, 2016				$ 135.6
Cash Investments				6.6	$ 3.5
Equity in ATC Earnings		$ 5.9	$ 6.1	17.3	$ 15.0
Equity Investment Balance as of September 30, 2017		$ 146.0		$ 146.0
FERC [Member] \| Return on Equity Complaint 2 [Member]
ALLETE's Investment in ATC [Roll Forward]
Proposed Return on Equity		9.70%		9.70%
Proposed Return on Equity, Including Incentive Adder		10.20%		10.20%
ATC [Member]
Investment in ATC [Line Items]
Ownership Percentage		8.00%		8.00%
Expected Additional Investment in 2017		$ 0.0		$ 0.0
ALLETE's Investment in ATC [Roll Forward]
Equity Investment Balance as of December 31, 2016				135.6
Cash Investments				6.6
Equity in ATC Earnings				17.3
Distributed ATC Earnings				(13.5)
Equity Investment Balance as of September 30, 2017		$ 146.0		$ 146.0
Authorized Return on Equity		10.32%	12.20%	10.32%	12.20%
Authorized Return on Equity, Including Incentive Adder		10.82%		10.82%
ATC [Member] \| Sensitivity Analysis [Member]
ALLETE's Investment in ATC [Roll Forward]
Basis Point Reduction on Approved Rate of Return on Common Equity		50		50
ATC [Member] \| Sensitivity Analysis [Member] \| After-tax [Member]
ALLETE's Investment in ATC [Roll Forward]
Annual Effect on Future Equity Earnings in ATC				$ 0.5
ATC [Member] \| Subsequent Event [Member]
ALLETE's Investment in ATC [Roll Forward]
Cash Investments	$ 1.2