Allowance for Doubtful Accounts - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Recoveries	$ 0.9	$ 0.8	$ 0.6
Provision for Bad Debt	6.7	5.6	5.5
Allowance for doubtful accounts	2.6	3.3	3.3	$ 1.0
Unbilled Revenues
Financing Receivable, Impaired [Line Items]
Allowance for doubtful accounts	0.1	0.2
Accounts Receivable
Financing Receivable, Impaired [Line Items]
Allowance for doubtful accounts	2.5	3.1
Regulatory Assets Harship Accounts
Financing Receivable, Impaired [Line Items]
Recoveries	5.8	7.9
Energy Commodity
Financing Receivable, Impaired [Line Items]
Provision for Bad Debt	$ 3.8	$ 2.4	$ 1.6