Fair Value of Financial Instruments - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Percentage of investment portfolio fair value pricing services or index price	90.20%	91.90%
Percentage of invested assets in total investment portfolio Level 3 recurring	5.60%
Net investment losses included in net income related to financial assets | $	$ (8.1)	$ (0.3)
Net investment (gains) losses included in net income related to financial liabilities | $	$ 10.0	$ 11.5
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Number of hard-to-value fixed maturity securities | security	150
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Number of hard-to-value fixed maturity securities | security	200