Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Policy loans	$ 11,679	$ 11,806
Cash and cash equivalents	2,090,514	1,069,211
Accrued investment income	110,380	121,604
Reinsurance recoverables	567,185	694,040
Receivables from parent and affiliates	114,230	87,620
Liabilities:
Long-term debt	299,747	299,747
Reinsurance payables	147,807	178,860
Fair Value
Assets:
Commercial mortgage and other loans	2,257,172	1,836,633
Policy loans	11,679	11,806
Short-term investments	0	165,000
Cash and cash equivalents	591,640	536,078
Accrued investment income	110,380	121,604
Reinsurance recoverables	50,683	51,225
Receivables from parent and affiliates	59,664	31,594
Other assets	438,668	672,424
Total assets	3,519,886	3,426,364
Liabilities:
Policyholders’ account balances - investment contracts	2,574,837	2,426,471
Short-term debt	0	121,205
Long-term debt	326,620	332,451
Reinsurance payables	42,146	44,446
Payables to parent and affiliates	34,272	47,345
Other liabilities	616,971	757,968
Separate account liabilities - investment contracts	17	30
Total liabilities	3,594,863	3,729,916
Carrying Amount
Assets:
Commercial mortgage and other loans	2,153,735	1,765,770
Policy loans	11,679	11,806
Short-term investments	0	165,000
Cash and cash equivalents	591,640	536,078
Accrued investment income	110,380	121,604
Reinsurance recoverables	49,793	50,484
Receivables from parent and affiliates	59,664	31,594
Other assets	438,668	672,424
Total assets	3,415,559	3,354,760
Liabilities:
Policyholders’ account balances - investment contracts	2,557,538	2,406,100
Short-term debt	0	119,671
Long-term debt	299,747	299,747
Reinsurance payables	42,146	44,446
Payables to parent and affiliates	34,272	47,345
Other liabilities	616,971	757,968
Separate account liabilities - investment contracts	17	30
Total liabilities	3,550,691	3,675,307
Level 1 | Fair Value
Assets:
Commercial mortgage and other loans	0	0
Policy loans	0	0
Short-term investments	0	165,000
Cash and cash equivalents	591,640	386,078
Accrued investment income	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	591,640	551,078
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Short-term debt	0	0
Long-term debt	0	0
Reinsurance payables	0	0
Payables to parent and affiliates	0	0
Other liabilities	0	0
Separate account liabilities - investment contracts	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	0	150,000
Accrued investment income	110,380	121,604
Reinsurance recoverables	0	0
Receivables from parent and affiliates	59,664	31,594
Other assets	20,698	278,355
Total assets	190,742	581,553
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Short-term debt	0	121,205
Long-term debt	326,620	332,451
Reinsurance payables	0	0
Payables to parent and affiliates	34,272	47,345
Other liabilities	616,971	757,968
Separate account liabilities - investment contracts	17	30
Total liabilities	977,880	1,258,999
Level 3 | Fair Value
Assets:
Commercial mortgage and other loans	2,257,172	1,836,633
Policy loans	11,679	11,806
Short-term investments	0	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Reinsurance recoverables	50,683	51,225
Receivables from parent and affiliates	0	0
Other assets	417,970	394,069
Total assets	2,737,504	2,293,733
Liabilities:
Policyholders’ account balances - investment contracts	2,574,837	2,426,471
Short-term debt	0	0
Long-term debt	0	0
Reinsurance payables	42,146	44,446
Payables to parent and affiliates	0	0
Other liabilities	0	0
Separate account liabilities - investment contracts	0	0
Total liabilities	$ 2,616,983	$ 2,470,917