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Equity Investments - Investment in Nobles 2 (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2023 USD ($) MW	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) MW	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Investment in Nobles 2 [Line Items]
Equity Investment Balance		$ 327.5		$ 327.5		$ 322.7
Cash Investments				4.3	$ 3.9
Equity Earnings		5.4	$ 5.3	11.4	10.8
Net Loss Attributable to Non-Controlling Interest		$ (10.8)	$ (16.8)	$ (31.4)	$ (36.6)
Nobles 2 [Member]
Investment in Nobles 2 [Line Items]
Ownership Percentage		49.00%		49.00%
Equity Investment Balance		$ 154.8		$ 154.8		$ 157.3
Distributed Earnings				(2.3)
Equity Earnings	[1]			(0.2)
Net Loss Attributable to Non-Controlling Interest				$ 5.9
Wind Turbine Generators [Member] | Tenaska [Member] | Minnesota Power [Member] | Tenaska PPA [Member]
Investment in Nobles 2 [Line Items]
Generating Capacity Counterparty Owned (MW) | MW		250		250
Long-term Contract for Purchase of Electric Power, Term of Contract (Years)				20 years
[1] The Company also recorded earnings from net loss attributable to non-controlling interest of $5.9 million related to its investment in Nobles 2.

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