Renewal term for a debt instrument disclosing for what period of time after maturity the instrument may be extended.

No definition available.

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- Definition

Purchase option to acquire an asset.

+ References

No definition available.

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- Definition

Unsecured Term Loan, Amount

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No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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No definition available.

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Description of reference rate used for variable rate of debt instrument.

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- Definition

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

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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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.

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- Definition

Amount of the required periodic payments including both interest and principal payments.

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- Definition

Amount, after accumulated amortization, of debt issuance costs classified as noncurrent. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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- References

No definition available.

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- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt classified as noncurrent. Excludes lease obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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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.

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- Definition

Amount of cash inflow from a noncontrolling interest. Includes, but is not limited to, purchase of additional shares or other increase in noncontrolling interest ownership.

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Short-Term and Long-Term Debt - Long-Term Debt (Details) $ in Millions			12 Months Ended
	Aug. 09, 2022 USD ($)	Feb. 28, 2022 USD ($)	Dec. 31, 2022 USD ($) Years	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Long-Term Debt			$ 1,648.2	$ 1,763.2
Long-Term Debt - Unamortized Debt Issuance Costs			8.2
Debt Instrument [Abstract]
Long-Term Debt Maturing in 2022			91.9
Long-Term Debt Maturing in 2023			94.8
Long-Term Debt Maturing in 2024			386.1
Long-Term Debt Maturing in 2025			79.4
Long-Term Debt Maturing in 2026			122.5
Long-Term Debt Maturing Thereafter			1,154.4
Proceeds from Non-Controlling Interest - Net of Issuance Costs			155.7	$ 90.9	$ 414.5
Camp Ripley Financing [Member]
Debt Instrument [Abstract]
Annual Financing Payment			$ 1.4
Financing Renewal Term (Years) \| Years			2
Purchase Option			$ 4.0
First Mortgage Bonds - 2.50% Due August 2030 [Member]
Debt Instrument [Abstract]
Interest Rate			4.08%
First Mortgage Bonds - 4.47% Series Due 2049 [Member]
Debt Instrument [Abstract]
Interest Rate			4.47%
First Mortgage Bonds - 4.07% Series Due 2048 [Member]
Debt Instrument [Abstract]
Interest Rate			4.07%
ALLETE Senior Unsecured Notes 3.11% Due 2027 [Member]
Debt Instrument [Abstract]
Interest Rate			3.11%
First Mortgage Bonds - 2.50% Series Due 2030
Debt Instrument [Abstract]
Interest Rate			2.50%
First Mortgage Bonds - 3.30% Series Due 2050
Debt Instrument [Abstract]
Interest Rate			3.30%
March Unsecured Term Loan Due in 2023
Debt Instrument [Abstract]
Unsecured Term Loan, Amount			$ 170.0
Debt Instrument, Description of Variable Rate Basis			SOFR
Debt Instrument, Basis Spread on Variable Rate			0.75%
ALLETE Bonds 4.54% Due August 2032
Debt Instrument [Abstract]
Proceeds from Issuance of First Mortgage Bond	$ 75.0
Interest Rate	4.54%
February Unsecured Term Loan Terminated in April 2022
Debt Instrument [Abstract]
Unsecured Term Loan, Amount		$ 175.0