Investments Investments, held in Trust or on Deposit (Details) - USD ($) $ in Millions |
Dec. 31, 2021 |
Dec. 31, 2020 |
---|---|---|
Deposit Assets [Abstract] | ||
Investments | $ 2,736.0 | $ 2,757.2 |
Assets Held-in-trust [Abstract] | ||
Funds held by or deposited with reinsurers | 3.1 | 3.2 |
Required by various state laws and regulations to hold securities or letters of credit in depository account [Member] | ||
Deposit Assets [Abstract] | ||
Investments | $ 861.4 | $ 768.7 |