Fair Values of Financial Instruments (Fair Values and Carrying Amounts of Financial Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Assets
Derivative instruments	$ 1,617,000	$ 1,207,288
Other investments	1,624,752	2,277,822
Coinsurance deposits	14,743,795	14,582,728
Market risk benefits	524,598	479,694
Liabilities
Policy benefit reserves	293,943	303,200
Market risk benefits	3,122,918	3,146,554
Carrying Amount
Assets
Fixed maturity securities, available for sale, fair value	32,044,379	34,780,482
Mortgage loans on real estate	7,281,831	7,537,594
Real estate investments	1,363,604	1,334,247
Limited partnerships and limited liability companies	501,084	506,685
Derivative instruments	1,617,000	1,207,288
Other investments	1,624,752	2,277,822
Cash and cash equivalents	13,495,847	9,772,586
Coinsurance deposits	14,743,795	14,582,728
Market risk benefits	524,598	479,694
Liabilities
Policy benefit reserves	60,638,086	60,549,922
Market risk benefits	3,122,918	3,146,554
Single premium immediate annuity (SPIA) benefit reserves	181,348	188,301
Notes and loan payable	783,791	785,443
Subordinated debentures	79,200	79,107
Fair Value
Assets
Fixed maturity securities, available for sale, fair value	32,044,379	34,780,482
Mortgage loans on real estate	6,777,489	7,047,993
Real estate investments	1,382,633	1,336,247
Limited partnerships and limited liability companies	501,084	506,685
Derivative instruments	1,617,000	1,207,288
Other investments	1,624,752	2,277,822
Cash and cash equivalents	13,495,847	9,772,586
Coinsurance deposits	13,671,767	13,570,942
Market risk benefits	524,598	479,694
Liabilities
Policy benefit reserves	56,103,251	56,366,631
Market risk benefits	3,122,918	3,146,554
Single premium immediate annuity (SPIA) benefit reserves	189,677	196,720
Notes and loan payable	775,660	770,570
Subordinated debentures	$ 86,095	$ 86,254