Summary of Significant Accounting Policies - Summary of Components of Benefit Obligation (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Regulatory Asset, Noncurrent	$ 577.6	$ 524.3
Pension Plan [Member] | Defined Benefit Plans Income Loss [Member]
Components of Benefit Obligation Regulatory Asset	75.9	110.0
Other Postretirement Benefits Plan [Member] | Defined Benefit Plans Income Loss [Member]
Components of Benefit Obligation Regulatory Asset	13.5	9.7
Benefit obligations regulatory asset [Member]
Regulatory Asset, Noncurrent	$ 89.4	$ 119.7