Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets [Abstract]
Policy loans	$ 489,592	$ 1,327,485
Cash and cash equivalents	1,789,752	918,931
Accrued investment income	161,703	160,027
Reinsurance recoverables	38,809,510	38,598,767
Receivables from parent and affiliates	197,904	278,131
Liabilities:
Cash collateral for loaned securities	150,666	3,004
Fair Value
Assets [Abstract]
Commercial mortgage and other loans	2,852,215	2,883,710
Policy loans	489,592	1,327,485
Short-term Investments	129,000	37,000
Cash and cash equivalents	872,309	482,299
Accrued investment income	161,703	160,027
Reinsurance recoverables	26,248	29,931
Receivables from parent and affiliates	46,958	116,086
Other assets	523,973	568,981
Total assets	5,101,998	5,605,519
Liabilities:
Policyholders’ account balances - investment contracts	3,905,233	3,947,337
Cash collateral for loaned securities	150,666	3,004
Long-term debt to affiliates	297,877	319,225
Payables to parent and affiliates	28,796	31,775
Other liabilities	846,393	898,879
Total liabilities	5,228,965	5,200,220
Carrying Amount
Assets [Abstract]
Commercial mortgage and other loans	3,066,931	2,832,560
Policy loans	489,592	1,327,485
Short-term Investments	129,000	37,000
Cash and cash equivalents	872,309	482,299
Accrued investment income	161,703	160,027
Reinsurance recoverables	27,938	28,883
Receivables from parent and affiliates	46,958	116,086
Other assets	523,973	568,981
Total assets	5,318,404	5,553,321
Liabilities:
Policyholders’ account balances - investment contracts	3,920,807	3,941,822
Cash collateral for loaned securities	150,666	3,004
Long-term debt to affiliates	315,807	320,362
Payables to parent and affiliates	28,796	31,775
Other liabilities	846,393	898,879
Total liabilities	5,262,469	5,195,842
Level 1 | Fair Value
Assets [Abstract]
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term Investments	129,000	37,000
Cash and cash equivalents	872,309	297,299
Accrued investment income	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	1,001,309	334,299
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Cash collateral for loaned securities	0	0
Long-term debt to affiliates	0	0
Payables to parent and affiliates	0	0
Other liabilities	0	0
Total liabilities	0	0
Level 2 | Fair Value
Assets [Abstract]
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term Investments	0	0
Cash and cash equivalents	0	185,000
Accrued investment income	161,703	160,027
Reinsurance recoverables	0	0
Receivables from parent and affiliates	46,958	116,086
Other assets	43,201	134,598
Total assets	251,862	595,711
Liabilities:
Policyholders’ account balances - investment contracts	1,285,380	1,356,850
Cash collateral for loaned securities	150,666	3,004
Long-term debt to affiliates	297,877	319,225
Payables to parent and affiliates	28,796	31,775
Other liabilities	813,143	864,788
Total liabilities	2,575,862	2,575,642
Level 3 | Fair Value
Assets [Abstract]
Commercial mortgage and other loans	2,852,215	2,883,710
Policy loans	489,592	1,327,485
Short-term Investments	0	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Reinsurance recoverables	26,248	29,931
Receivables from parent and affiliates	0	0
Other assets	480,772	434,383
Total assets	3,848,827	4,675,509
Liabilities:
Policyholders’ account balances - investment contracts	2,619,853	2,590,487
Cash collateral for loaned securities	0	0
Long-term debt to affiliates	0	0
Payables to parent and affiliates	0	0
Other liabilities	33,250	34,091
Total liabilities	$ 2,653,103	$ 2,624,578