Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Mar. 31, 2020		Dec. 31, 2019
Assets:
Policy loans	$ 1,317,110		$ 1,314,064
Cash and cash equivalents	555,352		563,199
Accrued investment income	89,492		89,448
Reinsurance recoverables	53,163,489	[1]	40,710,159
Receivables from parent and affiliates	249,827		271,981
Liabilities:
Cash collateral for loaned securities	2,587		7,529
Short-term debt	0		0
Fair Value
Assets:
Commercial mortgage and other loans	1,237,180		1,288,625
Policy loans	1,317,110		1,314,064
Cash and cash equivalents	25,393		15,557
Accrued investment income	89,492		89,448
Reinsurance recoverables	213,552		212,368
Receivables from parent and affiliates	134,288		149,415
Other assets	24,046		22,505
Total assets	3,041,061		3,091,982
Liabilities:
Policyholders’ account balances - investment contracts	1,556,133		1,541,910
Cash collateral for loaned securities	2,587		7,529
Short-term debt	0		2,845
Payables to parent and affiliates	199,644		216,842
Other liabilities	440,806		387,109
Total liabilities	2,199,170		2,156,235
Carrying Amount
Assets:
Commercial mortgage and other loans	1,206,707		1,239,885
Policy loans	1,317,110		1,314,064
Cash and cash equivalents	25,393		15,557
Accrued investment income	89,492		89,448
Reinsurance recoverables	214,349		211,813
Receivables from parent and affiliates	134,288		149,415
Other assets	24,046		22,505
Total assets	3,011,385		3,042,687
Liabilities:
Policyholders’ account balances - investment contracts	1,556,930		1,541,355
Cash collateral for loaned securities	2,587		7,529
Short-term debt	0		2,845
Payables to parent and affiliates	199,644		216,842
Other liabilities	440,806		387,109
Total liabilities	2,199,967		2,155,680
Level 1 | Fair Value
Assets:
Commercial mortgage and other loans	0		0
Policy loans	0		0
Cash and cash equivalents	25,393		15,557
Accrued investment income	0		0
Reinsurance recoverables	0		0
Receivables from parent and affiliates	0		0
Other assets	0		0
Total assets	25,393		15,557
Liabilities:
Policyholders’ account balances - investment contracts	0		0
Cash collateral for loaned securities	0		0
Short-term debt	0		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
Cash and cash equivalents	0		0
Accrued investment income	89,492		89,448
Reinsurance recoverables	0		0
Receivables from parent and affiliates	134,288		149,415
Other assets	24,046		22,505
Total assets	247,826		261,368
Liabilities:
Policyholders’ account balances - investment contracts	1,279,303		1,264,128
Cash collateral for loaned securities	2,587		7,529
Short-term debt	0		2,845
Payables to parent and affiliates	199,644		216,842
Other liabilities	440,806		387,109
Total liabilities	1,922,340		1,878,453
Level 3 | Fair Value
Assets:
Commercial mortgage and other loans	1,237,180		1,288,625
Policy loans	1,317,110		1,314,064
Cash and cash equivalents	0		0
Accrued investment income	0		0
Reinsurance recoverables	213,552		212,368
Receivables from parent and affiliates	0		0
Other assets	0		0
Total assets	2,767,842		2,815,057
Liabilities:
Policyholders’ account balances - investment contracts	276,830		277,782
Cash collateral for loaned securities	0		0
Short-term debt	0		0
Payables to parent and affiliates	0		0
Other liabilities	0		0
Total liabilities	$ 276,830		$ 277,782

[1] March 31, 2020 amounts include the impacts of the January 1, 2020 adoption of ASU 2016-13. See Note 2 for details.