Other Reinsurance (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) director employees	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Effects of Reinsurance [Line Items]
Ceded earned premiums	$ 42.7	$ 36.1	$ 31.2
Assumed earned premiums	26.3	34.7	50.8
Catastrophe Reinsurance
Effects of Reinsurance [Line Items]
Ceded earned premiums	32.0	30.3	26.7
Non-Catastrophe Reinsurance
Effects of Reinsurance [Line Items]
Assumed earned premiums	$ 41.4	56.7	73.8
Capitol County Mutual Fire Insurance Company
Effects of Reinsurance [Line Items]
Number of employee board members | employees	5
Number of board of director members | director	5
Old Reliable Casualty Company
Effects of Reinsurance [Line Items]
Number of employee board members | employees	9
Number of board of director members | director	9
Capitol County Mutual Fire Insurance Company
Effects of Reinsurance [Line Items]
Assumed earned premiums	$ 11.9	17.3	18.1
Capitol County Mutual Fire Insurance Company | Trinity
Effects of Reinsurance [Line Items]
Percentage of written business assumed	100.00%
Old Reliable Casualty Company
Effects of Reinsurance [Line Items]
Assumed earned premiums	$ 3.2	$ 4.7	$ 4.9
Old Reliable Casualty Company | Trinity
Effects of Reinsurance [Line Items]
Percentage of written business assumed	100.00%