Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Sep. 30, 2020		Dec. 31, 2019
Assets:
Policy loans	$ 1,322,235		$ 1,314,064
Cash and cash equivalents	633,712		563,199
Accrued investment income	90,451		89,448
Reinsurance recoverables	51,051,073	[1]	40,710,159
Receivables from parent and affiliates	286,986		271,981
Liabilities:
Cash collateral for loaned securities	2,731		7,529
Short-term debt	4,300		2,800
Fair Value
Assets:
Commercial mortgage and other loans	1,296,619		1,288,625
Policy loans	1,322,235		1,314,064
Cash and cash equivalents	28,709		15,557
Accrued investment income	90,451		89,448
Reinsurance recoverables	224,580		212,368
Receivables from parent and affiliates	173,347		149,415
Other assets	23,516		22,505
Total assets	3,159,457		3,091,982
Liabilities:
Policyholders’ account balances - investment contracts	1,664,357		1,541,910
Cash collateral for loaned securities	2,731		7,529
Short-term debt	4,297		2,845
Payables to parent and affiliates	73,332		216,842
Other liabilities	350,192		387,109
Total liabilities	2,094,909		2,156,235
Carrying Amount
Assets:
Commercial mortgage and other loans	1,227,120		1,239,885
Policy loans	1,322,235		1,314,064
Cash and cash equivalents	28,709		15,557
Accrued investment income	90,451		89,448
Reinsurance recoverables	216,235		211,813
Receivables from parent and affiliates	173,347		149,415
Other assets	23,516		22,505
Total assets	3,081,613		3,042,687
Liabilities:
Policyholders’ account balances - investment contracts	1,656,012		1,541,355
Cash collateral for loaned securities	2,731		7,529
Short-term debt	4,297		2,845
Payables to parent and affiliates	73,332		216,842
Other liabilities	350,192		387,109
Total liabilities	2,086,564		2,155,680
Level 1 | Fair Value
Assets:
Commercial mortgage and other loans	0		0
Policy loans	0		0
Cash and cash equivalents	28,709		15,557
Accrued investment income	0		0
Reinsurance recoverables	0		0
Receivables from parent and affiliates	0		0
Other assets	0		0
Total assets	28,709		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	90,451		89,448
Reinsurance recoverables	0		0
Receivables from parent and affiliates	173,347		149,415
Other assets	23,516		22,505
Total assets	287,314		261,368
Liabilities:
Policyholders’ account balances - investment contracts	1,380,211		1,264,128
Cash collateral for loaned securities	2,731		7,529
Short-term debt	4,297		2,845
Payables to parent and affiliates	73,332		216,842
Other liabilities	350,192		387,109
Total liabilities	1,810,763		1,878,453
Level 3 | Fair Value
Assets:
Commercial mortgage and other loans	1,296,619		1,288,625
Policy loans	1,322,235		1,314,064
Cash and cash equivalents	0		0
Accrued investment income	0		0
Reinsurance recoverables	224,580		212,368
Receivables from parent and affiliates	0		0
Other assets	0		0
Total assets	2,843,434		2,815,057
Liabilities:
Policyholders’ account balances - investment contracts	284,146		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	$ 284,146		$ 277,782

[1] September 30, 2020 amounts include the impacts of the January 1, 2020 adoption of ASU 2016-13. See Note 2 for details.