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Equity Investments - Investment in Nobles 2 (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022 USD ($) MW	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) MW	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Investment in Nobles 2 [Line Items]
Equity Investment Balance		$ 322.0		$ 322.0		$ 318.0
Cash Investments				3.9	$ 17.1
Equity Earnings		5.3	$ 5.1	10.8	9.9
Net Loss Attributable to Non-Controlling Interest		$ (16.8)	$ (6.2)	$ (36.6)	$ (14.6)
Nobles 2 [Member]
Investment in Nobles 2 [Line Items]
Ownership Percentage		49.00%		49.00%
Equity Investment Balance		$ 160.8		$ 160.8		$ 163.5
Distributed Earnings				(2.8)
Equity Earnings	[1]			0.1
Net Loss Attributable to Non-Controlling Interest				$ 6.2
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 net loss attributable to non-controlling interest of $6.2 million related to its investment in Nobles 2.

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