Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Assets:
Policy loans	$ 1,556,658	$ 1,541,480
Cash and cash equivalents	2,102,338	3,325,698
Accrued investment income	502,312	466,394
Reinsurance recoverables and deposit receivables	49,168,211	48,247,817
Receivables from parent and affiliates	641,061	678,028
Liabilities
Cash collateral for loaned securities	236,793	121,372
Fair Value
Assets:
Commercial mortgage and other loans	7,943,756	7,534,909
Policy loans	1,556,658	1,541,480
Short-term investments	101	21,101
Cash and cash equivalents	273,914	474,415
Accrued investment income	502,312	466,394
Reinsurance recoverables and deposit receivables	2,347,998	2,355,489
Receivables from parent and affiliates	74,030	157,566
Other assets	184,107	203,493
Total assets	12,882,876	12,754,847
Liabilities
Policyholders’ account balances - investment contracts	11,752,336	10,811,361
Cash collateral for loaned securities	236,793	121,372
Reinsurance and funds withheld payable	2,643,105	2,602,140
Payables to parent and affiliates	49,361	38,571
Other liabilities	925,587	880,884
Total liabilities	15,607,182	14,454,328
Carrying Amount
Assets:
Commercial mortgage and other loans	8,054,419	7,759,323
Policy loans	1,556,658	1,541,480
Short-term investments	101	21,101
Cash and cash equivalents	273,914	474,415
Accrued investment income	502,312	466,394
Reinsurance recoverables and deposit receivables	2,349,003	2,357,292
Receivables from parent and affiliates	74,030	157,566
Other assets	184,107	203,493
Total assets	12,994,544	12,981,064
Liabilities
Policyholders’ account balances - investment contracts	11,764,366	10,826,931
Cash collateral for loaned securities	236,793	121,372
Reinsurance and funds withheld payable	2,643,105	2,602,140
Payables to parent and affiliates	49,361	38,571
Other liabilities	925,587	880,884
Total liabilities	15,619,212	14,469,898
Level 1 | Fair Value
Assets:
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term investments	0	21,101
Cash and cash equivalents	263,914	474,415
Accrued investment income	0	0
Reinsurance recoverables and deposit receivables	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	263,914	495,516
Liabilities
Policyholders’ account balances - investment contracts	0	0
Cash collateral for loaned securities	0	0
Reinsurance and funds withheld payable	0	0
Payables to parent and affiliates	0	0
Other liabilities	0	0
Total liabilities	0	0
Level 2 | Fair Value
Assets:
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term investments	101	0
Cash and cash equivalents	10,000	0
Accrued investment income	502,312	466,394
Reinsurance recoverables and deposit receivables	0	0
Receivables from parent and affiliates	74,030	157,566
Other assets	184,107	203,493
Total assets	770,550	827,453
Liabilities
Policyholders’ account balances - investment contracts	803,362	815,520
Cash collateral for loaned securities	236,793	121,372
Reinsurance and funds withheld payable	2,643,105	2,602,140
Payables to parent and affiliates	49,361	38,571
Other liabilities	893,981	849,278
Total liabilities	4,626,602	4,426,881
Level 3 | Fair Value
Assets:
Commercial mortgage and other loans	7,943,756	7,534,909
Policy loans	1,556,658	1,541,480
Short-term investments	0	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Reinsurance recoverables and deposit receivables	2,347,998	2,355,489
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	11,848,412	11,431,878
Liabilities
Policyholders’ account balances - investment contracts	10,948,974	9,995,841
Cash collateral for loaned securities	0	0
Reinsurance and funds withheld payable	0	0
Payables to parent and affiliates	0	0
Other liabilities	31,606	31,606
Total liabilities	$ 10,980,580	$ 10,027,447