Investment Income and Gains and Losses (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) recognized during the period on equity securities still held	$ 6,000,000	$ (20,600,000)	$ 116,900,000
Fixed maturity securities on non-accrual	14,800,000	0
Impairment losses on investment securities	18,000,000	16,700,000	700,000
Impairments on fixed maturities credit related losses	6,900,000	3,700,000
Allowance for credit losses	10,000,000	3,200,000	7,100,000
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Impairment losses on investment securities		18,500,000	1,300,000
Fixed Maturities Intent to Sell Securities [Member]
Gain (Loss) on Investments [Line Items]
Impairment losses on investment securities	11,100,000	14,800,000
Mortgage Loans on Real Estate [Member]
Gain (Loss) on Investments [Line Items]
Impairment losses on investment securities			600,000
Impairments on fixed maturities partially offset by recoveries		1,800,000
Allowance for credit losses	10,000,000	3,200,000
Fixed Maturities Including Held For Sale [Member]
Gain (Loss) on Investments [Line Items]
Allowance for credit losses	1,900,000	2,100,000
Investments Net Asset Value [Member]
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) recognized during the period on equity securities still held	$ (8,100,000)	$ (2,000,000)	$ 17,100,000