Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Loss, LAE and unearned premium reserves, net	$ 185.6	$ 170.0
Investments, net	144.3
Employee benefit plans	8.4	7.2
Other	7.3	11.4
Total deferred tax assets	345.6	188.6
Deferred acquisition costs	127.0	115.9
Software capitalization	19.4	24.9
Investments, net		108.6
Total deferred tax liabilities	146.4	249.4
Net deferred tax asset	$ 199.2
Net deferred tax liability		$ (60.8)