Regulatory Assets and Liabilities - Regulatory Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Regulatory liabilities
Other current liabilities	$ 56.4	$ 14.3
Regulatory liabilities	3,735.5	3,946.0
Total regulatory liabilities	3,791.9	3,960.3
Income tax related items
Regulatory liabilities
Total regulatory liabilities	1,956.6	1,998.5
Removal costs
Regulatory liabilities
Total regulatory liabilities	1,260.9	1,248.0
Pension and OPEB benefits
Regulatory liabilities
Total regulatory liabilities	340.5	397.3
Derivatives
Regulatory liabilities
Total regulatory liabilities	76.7	124.1
Energy costs refundable through rate adjustments
Regulatory liabilities
Total regulatory liabilities	53.4	13.7
Uncollectible expense
Regulatory liabilities
Total regulatory liabilities	24.0	37.1
Earnings sharing mechanisms
Regulatory liabilities
Total regulatory liabilities	12.9	28.4
Electric transmission costs
Regulatory liabilities
Total regulatory liabilities	0.4	84.2
Amortization of transmission regulatory liabilities	81.0
Other, net
Regulatory liabilities
Total regulatory liabilities	$ 66.5	$ 29.0