Investments (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Schedule of Investments [Line Items]
Loans acquired	$ 5,403,100	$ 27,600	$ 5,403,100	$ 27,600
Loans sold	0	24,800	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	$ 2,215,649		2,215,649		2,353,479
Twelve Months or More, Gross Unrealized Losses	1,937,529		1,937,529		1,428,069
NAIC high or highest quality rating | Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Losses	2,071,000		2,071,000		2,164,100
NAIC other than high or highest quality rating | Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Losses	$ 144,700		$ 144,700		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)	$ (53,500)	(184,100)	$ 42,600	(520,500)
Other Income | Equity securities
Schedule of Investments [Line Items]
Net unrealized investment gains (losses)	(1,100)	$ (10,000)	8,100	$ (14,100)
Fixed maturities
Schedule of Investments [Line Items]
Twelve Months or More, Gross Unrealized Losses	$ 1,937,500		$ 1,937,500		$ 1,428,100