Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Commercial mortgage and other loans	$ 1,658,235	$ 1,681,553
Policy loans	1,143,303	1,123,912
Other long-term investments	379,237	298,143
Accrued investment income	100,031	90,506
Liabilities:
Cash collateral for loaned securities	40,416	65,418
Short-term debt to parent and affiliates	180,000	423,000
Long-term debt to parent and affiliates	1,204,000	1,288,000
Fair Value
Assets:
Commercial mortgage and other loans	1,710,491	1,784,435
Policy loans	1,143,303	1,123,912
Other long-term investments	27,346	11,085
Cash and cash equivalents	175,361	147,109
Accrued investment income	100,031	90,506
Receivables from parent and affiliates	65,628	70,668
Other assets	6,162	24,126
Total assets	3,228,322	3,251,841
Liabilities:
Policyholders’ account balances - investment contracts	1,184,744	969,757
Cash collateral for loaned securities	40,416	65,418
Short-term debt to parent and affiliates	180,105	429,903
Long-term debt to parent and affiliates	1,227,110	1,321,501
Payables to parent and affiliates	72,791	53,027
Other liabilities	343,089	315,736
Total liabilities	3,048,255	3,155,342
Fair Value | Level 1
Assets:
Commercial mortgage and other loans	0	0
Policy loans	0	0
Other long-term investments	0	0
Cash and cash equivalents	19,297	53,476
Accrued investment income	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	19,297	53,476
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Cash collateral for loaned securities	0	0
Short-term debt to parent and affiliates	0	0
Long-term debt to parent and affiliates	0	0
Payables to parent and affiliates	0	0
Other liabilities	0	0
Total liabilities	0	0
Fair Value | Level 2
Assets:
Commercial mortgage and other loans	8,540	8,486
Policy loans	0	0
Other long-term investments	0	0
Cash and cash equivalents	156,064	93,633
Accrued investment income	100,031	90,506
Receivables from parent and affiliates	65,628	70,668
Other assets	6,162	24,126
Total assets	336,425	287,419
Liabilities:
Policyholders’ account balances - investment contracts	947,853	929,694
Cash collateral for loaned securities	40,416	65,418
Short-term debt to parent and affiliates	180,105	429,903
Long-term debt to parent and affiliates	1,227,110	1,321,501
Payables to parent and affiliates	72,791	53,027
Other liabilities	343,089	315,736
Total liabilities	2,811,364	3,115,279
Fair Value | Level 3
Assets:
Commercial mortgage and other loans	1,701,951	1,775,949
Policy loans	1,143,303	1,123,912
Other long-term investments	27,346	11,085
Cash and cash equivalents	0	0
Accrued investment income	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	2,872,600	2,910,946
Liabilities:
Policyholders’ account balances - investment contracts	236,891	40,063
Cash collateral for loaned securities	0	0
Short-term debt to parent and affiliates	0	0
Long-term debt to parent and affiliates	0	0
Payables to parent and affiliates	0	0
Other liabilities	0	0
Total liabilities	236,891	40,063
Carrying Amount
Assets:
Commercial mortgage and other loans	1,658,235	1,681,553
Policy loans	1,143,303	1,123,912
Other long-term investments	26,395	10,168
Cash and cash equivalents	175,361	147,109
Accrued investment income	100,031	90,506
Receivables from parent and affiliates	65,628	70,689
Other assets	6,162	24,126
Total assets	3,175,115	3,148,063
Liabilities:
Policyholders’ account balances - investment contracts	1,190,596	976,190
Cash collateral for loaned securities	40,416	65,418
Short-term debt to parent and affiliates	180,000	423,000
Long-term debt to parent and affiliates	1,204,000	1,288,000
Payables to parent and affiliates	72,791	53,027
Other liabilities	343,089	315,736
Total liabilities	$ 3,030,892	$ 3,121,371