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Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other Commitments [Line Items]
Land easement non-lease payments expense	$ 1.3	$ 1.3	$ 0.6
Westmoreland Arbitration | Pending Litigation
Other Commitments [Line Items]
Recovery sought	$ 5.5
OTP | Coyote Station
Other Commitments [Line Items]
Ownership percentage	35.00%	35.00%
OTP | Federal Energy Regulatory Commission
Other Commitments [Line Items]
Estimated liability of refund obligation		$ 2.5
OTP | Construction Programs
Other Commitments [Line Items]
Long-term purchase commitment, amount	$ 68.0
Other commitments charged to rent expense	0.3	$ 0.1	$ 0.3
OTP | OTP Land Easements
Other Commitments [Line Items]
Long-term purchase commitment, amount	$ 34.5

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- Definition

Amount of non-lease land easement payments charged to rent expense in the Electric segment.

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Other Commitments, Expense

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- Definition

The proportionate share of interest (percent) in a jointly owned utility plant.

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-SubTopic 360
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- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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