Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Apr. 19, 2021
Non-cash transactions:
Capital expenditures included in current liabilities	$ 245.7	$ 170.4	$ 223.6
Assets acquired under a finance lease		59.3	26.4
Assets acquired under an operating lease		10.9	13.4
Reclassification of other property to regulatory assets	607.6	0.0	0.0
Assets recorded for asset retirement obligations	12.0	91.5	54.6
Obligation to the Developer	277.5	69.7	0.0
Purchase Contract Liability	129.4	0.0	0.0	$ 168.8
Schedule of interest and income taxes paid:
Cash paid for interest on long-term debt, net of interest capitalized amounts	322.4	349.0	349.7
Cash paid for interest on finance leases	9.4	11.1	11.3
Cash paid for income taxes, net of refunds(5)	$ 5.4	$ (1.0)	$ 10.8