Schedule I - Condensed Financial Information - Notes to Condensed Financial Statements (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 22, 2016
Parent Company and Unregulated Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Investments and cash	$ 83.2	$ 249.7
Regulated Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Investments and cash	$ 280.5	$ 224.8
Parent Company
Condensed Financial Statements, Captions [Line Items]
Surplus note			$ 40.0