Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Policy loans	$ 11,659	$ 11,806
Cash and cash equivalents	1,809,484	1,069,211
Accrued investment income	99,519	121,604
Reinsurance recoverables	543,849	694,040
Receivables from parent and affiliates	88,712	87,620
Liabilities:
Long-term debt	299,747	299,747
Reinsurance payables	160,279	178,860
Fair Value
Assets:
Commercial mortgage and other loans	1,861,808	1,836,633
Policy loans	11,659	11,806
Short-term investments	0	165,000
Cash and cash equivalents	738,682	536,078
Accrued investment income	99,519	121,604
Reinsurance recoverables	51,462	51,225
Receivables from parent and affiliates	34,565	31,594
Other assets	482,996	672,424
Total assets	3,280,691	3,426,364
Liabilities:
Policyholders’ account balances - investment contracts	2,515,936	2,426,471
Short-term debt	120,394	121,205
Long-term debt	328,773	332,451
Reinsurance payables	43,550	44,446
Payables to parent and affiliates	40,074	47,345
Other liabilities	537,517	757,968
Separate account liabilities - investment contracts	24	30
Total liabilities	3,586,268	3,729,916
Carrying Amount
Assets:
Commercial mortgage and other loans	1,794,798	1,765,770
Policy loans	11,659	11,806
Short-term investments	0	165,000
Cash and cash equivalents	738,682	536,078
Accrued investment income	99,519	121,604
Reinsurance recoverables	50,695	50,484
Receivables from parent and affiliates	34,565	31,594
Other assets	482,996	672,424
Total assets	3,212,914	3,354,760
Liabilities:
Policyholders’ account balances - investment contracts	2,502,017	2,406,100
Short-term debt	119,671	119,671
Long-term debt	299,747	299,747
Reinsurance payables	43,550	44,446
Payables to parent and affiliates	40,074	47,345
Other liabilities	537,517	757,968
Separate account liabilities - investment contracts	24	30
Total liabilities	3,542,600	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	478,682	386,078
Accrued investment income	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	478,682	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	260,000	150,000
Accrued investment income	99,519	121,604
Reinsurance recoverables	0	0
Receivables from parent and affiliates	34,565	31,594
Other assets	72,976	278,355
Total assets	467,060	581,553
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Short-term debt	120,394	121,205
Long-term debt	328,773	332,451
Reinsurance payables	0	0
Payables to parent and affiliates	40,074	47,345
Other liabilities	537,517	757,968
Separate account liabilities - investment contracts	24	30
Total liabilities	1,026,782	1,258,999
Level 3 | Fair Value
Assets:
Commercial mortgage and other loans	1,861,808	1,836,633
Policy loans	11,659	11,806
Short-term investments	0	0
Cash and cash equivalents	0	0
Accrued investment income	0	0
Reinsurance recoverables	51,462	51,225
Receivables from parent and affiliates	0	0
Other assets	410,020	394,069
Total assets	2,334,949	2,293,733
Liabilities:
Policyholders’ account balances - investment contracts	2,515,936	2,426,471
Short-term debt	0	0
Long-term debt	0	0
Reinsurance payables	43,550	44,446
Payables to parent and affiliates	0	0
Other liabilities	0	0
Separate account liabilities - investment contracts	0	0
Total liabilities	$ 2,559,486	$ 2,470,917