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Short-Term and Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	6 Months Ended				0 Months Ended				0 Months Ended		0 Months Ended		0 Months Ended		0 Months Ended
	Jun. 27, 2014	Jun. 30, 2014	Jan. 30, 2014	Dec. 31, 2013	Dec. 31, 2013 ALLETE Bonds 4.86% Series Due 2013 [Member]	Mar. 04, 2014 ALLETE Bonds 3.69% Due March2024 [Member]	Mar. 04, 2014 ALLETE Bonds 4.95% Due March2044 [Member]	Jun. 26, 2014 ALLETE Bonds 3.40% Due July2022 [Member]	Jun. 26, 2014 ALLETE Bonds 3.40% Due July2022 [Member]	Jun. 26, 2014 ALLETE Bonds 5.05% Due July2044 [Member]	Jun. 26, 2014 ALLETE Bonds 5.05% Due July2044 [Member]	Jun. 27, 2014 ALLETE Bonds 3.02% Due September 2021 [Member]	Jun. 27, 2014 ALLETE Bonds 3.02% Due September 2021 [Member]	Jun. 27, 2014 ALLETE Bonds 3.74% Due September 2029 [Member]	Jun. 27, 2014 ALLETE Bonds 3.74% Due September 2029 [Member]	Jun. 27, 2014 ALLETE Bonds 4.39% Due September 2044 [Member]	Jun. 27, 2014 ALLETE Bonds 4.39% Due September 2044 [Member]	Jul. 01, 2014 Subsequent Event [Member] 4.95% Pollution Control Series F Due 2022 [Member]
Debt Instrument [Line Items]
Short-Term Debt Outstanding		$ 10.8		$ 27.2
Short-Term Debt Outstanding, Subsequently Matured		10.8		27.2	18.0
Long-Term Debt Outstanding		1,316.8		1,083.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			23.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-term Debt			2.2
Long-term Debt		1,327.6		1,110.2														111.0
Proceeds from Issuance of First Mortgage Bonds		215.0				60.0	40.0	75.0		40.0
Debt Instrument, Interest Rate, Stated Percentage						3.69%	4.95%		3.40%		5.05%
Expected Proceeds from Future Issuance of First Mortgage Bonds	$ 160.0											$ 60.0		$ 50.0		$ 50.0
Future Debt Instrument, Interest Rate, Stated Percentage													3.02%		3.74%		4.39%

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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Long-term Debt, Including current portion

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The expected cash inflow from amounts received from a future long-term debt instrument issuance 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.

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Contractual interest rate for funds borrowed, under the debt agreement, which will take place in the future.

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Amount of long-term debt due within one year or within the normal operating cycle, if longer, assumed at the acquisition date.

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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.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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