Income Tax Expense (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current Income Tax Expense [Abstract]
Federal	[1]	$ 1.2	$ 0.0	$ 0.0
State	[1]	6.1	0.0	0.0
Total Current Income Tax Expense	[1]	7.3	0.0	0.0
Deferred Income Tax Expense (Benefit) [Abstract]
Federal	[2]	(32.8)	(37.2)	(51.5)
State	[3]	(5.2)	10.8	8.6
Investment Tax Credit Amortization		(0.5)	(0.5)	(0.5)
Total Deferred Income Tax Expense (Benefit)		(38.5)	(26.9)	(43.4)
Total Income Tax Expense (Benefit)		$ (31.2)	$ (26.9)	$ (43.4)

[1] For the years ended December 31, 2021 and 2020, the federal and state current tax expense was minimal due to NOLs which resulted from the bonus depreciation provisions of certain tax legislation. Federal and state NOLs are being carried forward to offset current and future taxable income. For the year ended December 31, 2022, federal NOLs were fully utilized and production tax credits were used to partially offset federal taxable income.

[2] For the years ended December 31, 2022, 2021 and 2020, the federal tax benefit is primarily due to production tax credits.

[3] For the year ended December 31, 2022, the state impact includes the benefit of deferred repricing as a result of the New Energy acquisition