Reinsurance - Unsecured Reinsurance Recoverable by Reinsurer (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Ceded Credit Risk [Line Items]
Reinsurance recoverable	$ 156.8	$ 89.8
Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	159.6	100.3
Lloyd's Underwriter Syndicate No. 1084 CSL | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	4.3	4.4
Lloyd's Underwriter Syndicate no. 2791 MAP | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	1.0	0.0
Lloyd's Underwriter Syndicate no. 2001 AML | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	0.5	0.7
Top Reinsurers | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	158.9	94.1
Other reinsurers | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	0.7	6.2
A+ | Hannover Rueck SE | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	100.1	60.2
A+ | Swiss Reinsurance America Corporation | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	27.6	12.4
A+ | Munich Reinsurance America Inc | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	0.4	0.6
A | MAPFRE Re, Compania De Reaseguros S.A. | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	23.8	14.4
A | Lloyd's Underwriter Syndicate no. 0033 HIS | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	0.4	0.8
A | Lloyd's Underwriter Syndicate no. 2357 NCL | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	0.4	0.6
A++ | General Reinsurance Corporation | Ceded Credit Risk, Unsecured
Ceded Credit Risk [Line Items]
Reinsurance recoverable	$ 0.4	$ 0.0