Quantitative Information Regarding Significant Unobservable Inputs (Details) $ in Millions		Dec. 31, 2021 USD ($) Rate	Dec. 31, 2020 USD ($) Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities | $		$ 33.7	$ 28.3
Fair Value, Inputs, Level 3 | Discounted Cash Flow | Embedded Derivative in Modified Coinsurance Arrangement
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded Derivative in Modified Coinsurance Arrangement | $	[1]	(30.1)	(39.8)
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private | $	[2]	$ 111.8	$ 45.7	[3],[4]
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Minimum | Lack of Marketability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.0014
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Minimum | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.0630	0.0050
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Maximum | Lack of Marketability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.0073
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Maximum | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.0630	0.2490
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Weighted Average | Lack of Marketability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.0051
Fair Value, Inputs, Level 3 | All Other Corporate Bonds | Market Approach | Weighted Average | Volatility of Credit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
All Other Corporate Bonds - Private, Measurement Input		0.0630	0.0363
Fair Value, Inputs, Level 3 | Perpetual Preferred Securities | Market Approach
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Securities | $	[3]	$ 5.8	$ 4.7

[1] Represents various actuarial assumptions required to derive the liability cash flows. Fair value of embedded derivative is most often driven by the change in the weighted average credit spread to the swap curve for the assets backing the hypothetical loan.

[2] Represents basis point adjustments for credit-specific factors

[3] Represents a decision to price based on par value, cost, or owner's equity when limited data is available

[4] Represents basis point adjustments to apply a discount due to the illiquidity of an investment