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Income Taxes: Income Taxes (Paid) Received (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Federal:
Total Federal	$ 12.5	$ 15.1
State:
Total State	(3.7)	(0.7)	$ (1.0)
Total income taxes (paid) received	8.8	14.4	(1.0)
Direct Payments Net of Refunds
Federal:
Total Federal	(3.5)	(0.9)
Transferred Renewable Credits Net of Discount
Federal:
Total Federal	16.0	16.0
Other
State:
Total State		(0.2)
Arkansas
State:
Total State	(0.7)
Colorado
State:
Total State	(0.6)	(0.2)
Kansas
State:
Total State			(0.2)
Nebraska
State:
Total State	$ (2.4)	$ (0.3)	$ (0.8)