Property and Casualty Insurance Reserves - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Losses and LAE Related to Prior Years	$ (158.5)	$ 22.5
Personal Automobile
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Losses and LAE Related to Prior Years	(110.9)	31.6
Preferred Automobile [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Losses and LAE Related to Prior Years	(18.3)	(1.9)
Homeowners [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Losses and LAE Related to Prior Years	(3.8)	(6.1)
Other Personal Lines [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Losses and LAE Related to Prior Years	(3.3)	(5.8)
Commercial Automobile
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Losses and LAE Related to Prior Years	$ (22.2)	$ (7.5)