Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Policy loans	$ 1,140,736	$ 1,123,912
Other long-term investments	308,987	298,143
Accrued investment income	96,356	90,506
Liabilities:
Cash collateral for loaned securities	69,296	65,418
Short-term debt	294,000	423,000
Long-term debt	1,281,000	1,288,000
Fair Value
Assets:
Commercial mortgage and other loans	1,775,987	1,784,435
Policy loans	1,140,736	1,123,912
Other long-term investments	20,802	11,085
Cash and cash equivalents	327,415	147,109
Accrued investment income	96,356	90,506
Receivables from parent and affiliates	110,833	70,668
Other assets	27,651	24,126
Total assets	3,499,780	3,251,841
Liabilities:
Policyholders’ account balances - investment contracts	1,155,610	969,757
Cash collateral for loaned securities	69,296	65,418
Short-term debt	296,278	429,903
Long-term debt	1,512,547	1,321,501
Payables to parent and affiliates	62,937	53,027
Other liabilities	326,316	315,736
Total liabilities	3,422,984	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	19,543	53,476
Accrued investment income	0	0
Receivables from parent and affiliates	0	0
Other assets	0	0
Total assets	19,543	53,476
Liabilities:
Policyholders’ account balances - investment contracts	0	0
Cash collateral for loaned securities	0	0
Short-term debt	0	0
Long-term debt	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	8,647	8,486
Policy loans	0	0
Other long-term investments	0	0
Cash and cash equivalents	307,872	93,633
Accrued investment income	96,356	90,506
Receivables from parent and affiliates	110,833	70,668
Other assets	27,651	24,126
Total assets	551,359	287,419
Liabilities:
Policyholders’ account balances - investment contracts	916,013	929,694
Cash collateral for loaned securities	69,296	65,418
Short-term debt	296,278	429,903
Long-term debt	1,512,547	1,321,501
Payables to parent and affiliates	62,937	53,027
Other liabilities	326,316	315,736
Total liabilities	3,183,387	3,115,279
Fair Value | Level 3
Assets:
Commercial mortgage and other loans	1,767,340	1,775,949
Policy loans	1,140,736	1,123,912
Other long-term investments	20,802	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	2,928,878	2,910,946
Liabilities:
Policyholders’ account balances - investment contracts	239,597	40,063
Cash collateral for loaned securities	0	0
Short-term debt	0	0
Long-term debt	0	0
Payables to parent and affiliates	0	0
Other liabilities	0	0
Total liabilities	239,597	40,063
Carrying Amount
Assets:
Commercial mortgage and other loans	1,709,477	1,681,553
Policy loans	1,140,736	1,123,912
Other long-term investments	20,016	10,168
Cash and cash equivalents	327,415	147,109
Accrued investment income	96,356	90,506
Receivables from parent and affiliates	110,833	70,689
Other assets	27,651	24,126
Total assets	3,432,484	3,148,063
Liabilities:
Policyholders’ account balances - investment contracts	1,161,766	976,190
Cash collateral for loaned securities	69,296	65,418
Short-term debt	294,000	423,000
Long-term debt	1,281,000	1,288,000
Payables to parent and affiliates	62,937	53,027
Other liabilities	326,316	315,736
Total liabilities	$ 3,195,315	$ 3,121,371