Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Assets:
Policy loans	$ 1,511,288	$ 1,472,677
Cash and cash equivalents	2,886,207	2,139,792
Accrued investment income	426,302	333,838
Reinsurance recoverables	40,693,991	38,709,651
Receivables from parent and affiliates	416,539	332,583
Liabilities
Cash collateral for loaned securities	19,397	218,310
Fair Value
Assets:
Commercial mortgage and other loans	6,465,057	5,918,386
Policy loans	1,511,288	1,472,677
Short-term investments	58,102	66,500
Cash and cash equivalents	1,217,653	495,667
Accrued investment income	426,302	333,838
Reinsurance recoverables	21,733	22,155
Receivables from parent and affiliates	85,725	184,599
Other assets	1,999,808	1,570,629
Total assets	11,785,668	10,064,451
Liabilities
Policyholders’ account balances - investment contracts	8,721,934	6,352,532
Cash collateral for loaned securities	19,397	218,310
Short-term debt to affiliates		176,110
Payables to parent and affiliates	26,493	16,573
Other liabilities	2,614,523	2,154,284
Total liabilities	11,382,347	8,917,809
Carrying Amount
Assets:
Commercial mortgage and other loans	6,718,386	6,122,721
Policy loans	1,511,288	1,472,677
Short-term investments	58,102	66,500
Cash and cash equivalents	1,217,653	495,667
Accrued investment income	426,302	333,838
Reinsurance recoverables	23,508	23,537
Receivables from parent and affiliates	85,725	184,599
Other assets	1,999,808	1,570,629
Total assets	12,040,772	10,270,168
Liabilities
Policyholders’ account balances - investment contracts	8,739,221	6,368,061
Cash collateral for loaned securities	19,397	218,310
Short-term debt to affiliates		180,411
Payables to parent and affiliates	26,493	16,573
Other liabilities	2,614,523	2,154,283
Total liabilities	11,399,634	8,937,638
Level 1 | Fair Value
Assets:
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term investments	58,102	66,500
Cash and cash equivalents	892,653	470,668
Accrued investment income	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	950,755	537,168
Liabilities
Policyholders’ account balances - investment contracts	0	0
Cash collateral for loaned securities	0	0
Short-term debt to affiliates		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	0	0
Cash and cash equivalents	325,000	24,999
Accrued investment income	426,302	333,838
Reinsurance recoverables	0	0
Receivables from parent and affiliates	85,725	184,599
Other assets	89,182	80,646
Total assets	926,209	624,082
Liabilities
Policyholders’ account balances - investment contracts	872,062	955,647
Cash collateral for loaned securities	19,397	218,310
Short-term debt to affiliates		176,110
Payables to parent and affiliates	26,493	16,573
Other liabilities	2,582,917	2,121,861
Total liabilities	3,500,869	3,488,501
Level 3 | Fair Value
Assets:
Commercial mortgage and other loans	6,465,057	5,918,386
Policy loans	1,511,288	1,472,677
Short-term investments	0	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Reinsurance recoverables	21,733	22,155
Receivables from parent and affiliates	0	0
Other assets	1,910,626	1,489,983
Total assets	9,908,704	8,903,201
Liabilities
Policyholders’ account balances - investment contracts	7,849,872	5,396,885
Cash collateral for loaned securities	0	0
Short-term debt to affiliates		0
Payables to parent and affiliates	0	0
Other liabilities	31,606	32,423
Total liabilities	$ 7,881,478	$ 5,429,308