Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Assets:
Policy loans	$ 1,524,636	$ 1,472,677
Cash and cash equivalents	3,313,710	2,139,792
Accrued investment income	444,591	333,838
Reinsurance recoverables	43,285,050	38,709,651
Receivables from parent and affiliates	618,259	332,583
Liabilities
Cash collateral for loaned securities	330,370	218,310
Fair Value
Assets:
Commercial mortgage and other loans	7,166,012	5,918,386
Policy loans	1,524,636	1,472,677
Short-term investments	34,101	66,500
Cash and cash equivalents	1,618,092	495,667
Accrued investment income	444,591	333,838
Reinsurance recoverables	23,875	22,155
Receivables from parent and affiliates	127,113	184,599
Other assets	2,191,476	1,570,629
Total assets	13,129,896	10,064,451
Liabilities
Policyholders’ account balances - investment contracts	9,886,939	6,352,532
Cash collateral for loaned securities	330,370	218,310
Short-term debt to affiliates		176,110
Payables to parent and affiliates	70,009	16,573
Other liabilities	3,056,495	2,154,284
Total liabilities	13,343,813	8,917,809
Carrying Amount
Assets:
Commercial mortgage and other loans	7,223,568	6,122,721
Policy loans	1,524,636	1,472,677
Short-term investments	34,101	66,500
Cash and cash equivalents	1,618,092	495,667
Accrued investment income	444,591	333,838
Reinsurance recoverables	25,147	23,537
Receivables from parent and affiliates	127,113	184,599
Other assets	2,191,476	1,570,629
Total assets	13,188,724	10,270,168
Liabilities
Policyholders’ account balances - investment contracts	9,899,498	6,368,061
Cash collateral for loaned securities	330,370	218,310
Short-term debt to affiliates		180,411
Payables to parent and affiliates	70,009	16,573
Other liabilities	3,056,495	2,154,283
Total liabilities	13,356,372	8,937,638
Level 1 | Fair Value
Assets:
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term investments	34,101	66,500
Cash and cash equivalents	1,343,092	470,668
Accrued investment income	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	1,377,193	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	275,000	24,999
Accrued investment income	444,591	333,838
Reinsurance recoverables	0	0
Receivables from parent and affiliates	127,113	184,599
Other assets	39,144	80,646
Total assets	885,848	624,082
Liabilities
Policyholders’ account balances - investment contracts	836,916	955,647
Cash collateral for loaned securities	330,370	218,310
Short-term debt to affiliates		176,110
Payables to parent and affiliates	70,009	16,573
Other liabilities	3,024,889	2,121,861
Total liabilities	4,262,184	3,488,501
Level 3 | Fair Value
Assets:
Commercial mortgage and other loans	7,166,012	5,918,386
Policy loans	1,524,636	1,472,677
Short-term investments	0	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Reinsurance recoverables	23,875	22,155
Receivables from parent and affiliates	0	0
Other assets	2,152,332	1,489,983
Total assets	10,866,855	8,903,201
Liabilities
Policyholders’ account balances - investment contracts	9,050,023	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	$ 9,081,629	$ 5,429,308