Investment Income and Gains and Losses (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) recognized during the period on equity securities still held	$ 33,200,000	$ 103,700,000	$ (39,500,000)
Impairment losses on investment securities	26,300,000	2,000,000.0	4,600,000
Impairments on fixed maturities included intend to sell	16,500,000
Impairments on fixed maturities credit related losses	1,100,000
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Impairment losses on investment securities	17,600,000		2,600,000
Mortgage Loans [Member]
Gain (Loss) on Investments [Line Items]
Impairment losses on investment securities	6,700,000
Allowance for credit losses	7,900,000	1,300,000
Other Invested Assets [Member]
Gain (Loss) on Investments [Line Items]
Impairment losses on investment securities			2,000,000.0
Fixed Maturities Including Held For Sale [Member]
Gain (Loss) on Investments [Line Items]
Allowance for credit losses	100,000	0
Fair Value Measured Using NAV [Member]
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) recognized during the period on equity securities still held	$ (6,900,000)	$ (4,600,000)	$ 5,300,000