Goodwill and Intangible Assets - Goodwill Rollforward (Details) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 43.5
Impairment	0.0
Acquisition	12.8
Ending balance	56.3
Property & Casualty
Goodwill [Roll Forward]
Beginning balance	9.5
Impairment	0.0
Acquisition	0.0
Ending balance	9.5
Life & Retirement
Goodwill [Roll Forward]
Beginning balance	14.4
Impairment	0.0
Acquisition	0.0
Ending balance	14.4
Supplemental & Group Benefits
Goodwill [Roll Forward]
Beginning balance	19.6
Impairment	0.0
Acquisition	12.8
Ending balance	$ 32.4