Investments (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Schedule of Investments [Line Items]
Loans acquired	$ 0	$ 0	$ 0	$ 27,600
Loans sold	0	0	0	24,800
Fixed maturity purchased with credit deterioration			0		$ 0
Accrued Investment Income Write Down	0	0	0	0
Securities sold under agreements to repurchase	$ 0		$ 0		$ 0
Commercial mortgage loans, Percentage	100.00%		100.00%		100.00%
Commercial mortgage and other loans purchased with credit deterioration			$ 0		$ 0
Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Losses	$ 2,930,818		2,930,818		2,353,479
Twelve Months or More, Gross Unrealized Losses	2,566,037		2,566,037		1,428,069
NAIC high or highest quality rating | Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Losses	2,754,100		2,754,100		2,164,100
NAIC other than high or highest quality rating | Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Losses	$ 176,700		$ 176,700		189,400
California
Schedule of Investments [Line Items]
Commercial mortgage loans, Percentage	29.00%		29.00%
Texas
Schedule of Investments [Line Items]
Commercial mortgage loans, Percentage	12.00%		12.00%
New York
Schedule of Investments [Line Items]
Commercial mortgage loans, Percentage	5.00%		5.00%
Europe
Schedule of Investments [Line Items]
Commercial mortgage loans, Percentage	9.00%		9.00%
Mexico
Schedule of Investments [Line Items]
Commercial mortgage loans, Percentage	2.00%		2.00%
Australia
Schedule of Investments [Line Items]
Commercial mortgage loans, Percentage	1.00%		1.00%
Other Income | Fixed maturities | Trading
Schedule of Investments [Line Items]
Net unrealized investment gains (losses)	$ (221,600)	(194,600)	$ (179,000)	(715,100)
Other Income | Equity securities
Schedule of Investments [Line Items]
Net unrealized investment gains (losses)	(10,900)	$ (10,200)	(2,800)	$ (24,300)
Fixed maturities
Schedule of Investments [Line Items]
Twelve Months or More, Gross Unrealized Losses	$ 2,566,000		$ 2,566,000		$ 1,428,100