Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets [Abstract]
Policy loans	$ 476,038	$ 1,327,485
Cash and cash equivalents	1,832,067	918,931
Accrued investment income	138,781	160,027
Reinsurance recoverables	39,356,117	38,598,767
Receivables from parent and affiliates	359,219	278,131
Liabilities:
Cash collateral for loaned securities	2,696	3,004
Fair Value
Assets [Abstract]
Commercial mortgage and other loans	2,877,680	2,883,710
Policy loans	476,038	1,327,485
Short-term Investments	19,000	37,000
Cash and cash equivalents	875,408	482,299
Accrued investment income	138,781	160,027
Reinsurance recoverables	27,530	29,931
Receivables from parent and affiliates	203,374	116,086
Other assets	463,065	568,981
Total assets	5,080,876	5,605,519
Liabilities:
Policyholders’ account balances - investment contracts	3,904,263	3,947,337
Cash collateral for loaned securities	2,696	3,004
Long-term debt to affiliates	307,832	319,225
Payables to parent and affiliates	132,405	31,775
Other liabilities	908,124	898,879
Total liabilities	5,255,320	5,200,220
Carrying Amount
Assets [Abstract]
Commercial mortgage and other loans	2,977,138	2,832,560
Policy loans	476,038	1,327,485
Short-term Investments	19,000	37,000
Cash and cash equivalents	875,408	482,299
Accrued investment income	138,781	160,027
Reinsurance recoverables	28,317	28,883
Receivables from parent and affiliates	203,374	116,086
Other assets	463,065	568,981
Total assets	5,181,121	5,553,321
Liabilities:
Policyholders’ account balances - investment contracts	3,912,340	3,941,822
Cash collateral for loaned securities	2,696	3,004
Long-term debt to affiliates	318,088	320,362
Payables to parent and affiliates	132,405	31,775
Other liabilities	908,124	898,879
Total liabilities	5,273,653	5,195,842
Level 1 | Fair Value
Assets [Abstract]
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term Investments	19,000	37,000
Cash and cash equivalents	575,408	297,299
Accrued investment income	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	594,408	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	300,000	185,000
Accrued investment income	138,781	160,027
Reinsurance recoverables	0	0
Receivables from parent and affiliates	203,374	116,086
Other assets	24,635	134,598
Total assets	666,790	595,711
Liabilities:
Policyholders’ account balances - investment contracts	1,323,368	1,356,850
Cash collateral for loaned securities	2,696	3,004
Long-term debt to affiliates	307,832	319,225
Payables to parent and affiliates	132,405	31,775
Other liabilities	874,033	864,788
Total liabilities	2,640,334	2,575,642
Level 3 | Fair Value
Assets [Abstract]
Commercial mortgage and other loans	2,877,680	2,883,710
Policy loans	476,038	1,327,485
Short-term Investments	0	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Reinsurance recoverables	27,530	29,931
Receivables from parent and affiliates	0	0
Other assets	438,430	434,383
Total assets	3,819,678	4,675,509
Liabilities:
Policyholders’ account balances - investment contracts	2,580,895	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	34,091	34,091
Total liabilities	$ 2,614,986	$ 2,624,578