Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Assets:
Policy loans	$ 11,957		$ 14,316
Accrued investment income	44,656		59,033
Liabilities:
Cash collateral for loaned securities	38,976		125,884
Short-term debt	0		27,803
Long-term debt	400,000		600,000
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets:
Commercial mortgage and other loans	426,981	[1]	449,359
Policy loans	11,957	[1]	14,316
Cash	266	[1]	749
Accrued investment income	44,656	[1]	59,033
Other assets	12,609	[1]	12,237
Total Assets Financial Instruments Not Carried At Fair Value	496,469	[1]	535,694
Liabilities:
Investment contracts- policyholders' account balances	75,242	[1]	66,176
Cash collateral for loaned securities	38,976	[1]	125,884
Short-term debt	0	[1]	27,803
Long-term debt	400,000	[1]	600,000
Other liabilities	194,047	[1]	169,139
Separate account liabilities - investment contracts	964	[1]	1,192
Total Financial Instrument Liabilities Not Carried At Fair Value	709,229	[1]	990,194
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets:
Commercial mortgage and other loans	473,964		490,151
Policy loans	11,957		14,316
Cash	266		749
Accrued investment income	44,656		59,033
Other assets	12,609		12,237
Total Assets Financial Instruments Not Carried At Fair Value	543,452		576,486
Liabilities:
Investment contracts- policyholders' account balances	78,159		66,659
Cash collateral for loaned securities	38,976		125,884
Short-term debt	0		27,803
Long-term debt	426,827		627,415
Other liabilities	194,047		169,139
Separate account liabilities - investment contracts	964		1,192
Total Financial Instrument Liabilities Not Carried At Fair Value	738,973		1,018,092
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 1 [Member]
Assets:
Commercial mortgage and other loans	0
Policy loans	0
Cash	266
Accrued investment income	0
Other assets	0
Total Assets Financial Instruments Not Carried At Fair Value	266
Liabilities:
Investment contracts- policyholders' account balances	0
Cash collateral for loaned securities	0
Short-term debt	0
Long-term debt	0
Other liabilities	0
Separate account liabilities - investment contracts	0
Total Financial Instrument Liabilities Not Carried At Fair Value	0
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Assets:
Commercial mortgage and other loans	0
Policy loans	0
Cash	0
Accrued investment income	44,656
Other assets	10,614
Total Assets Financial Instruments Not Carried At Fair Value	55,270
Liabilities:
Investment contracts- policyholders' account balances	0
Cash collateral for loaned securities	38,976
Short-term debt	0
Long-term debt	426,827
Other liabilities	194,047
Separate account liabilities - investment contracts	964
Total Financial Instrument Liabilities Not Carried At Fair Value	660,814
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 3 [Member]
Assets:
Commercial mortgage and other loans	473,964
Policy loans	11,957
Cash	0
Accrued investment income	0
Other assets	1,995
Total Assets Financial Instruments Not Carried At Fair Value	487,916
Liabilities:
Investment contracts- policyholders' account balances	78,159
Cash collateral for loaned securities	0
Short-term debt	0
Long-term debt	0
Other liabilities	0
Separate account liabilities - investment contracts	0
Total Financial Instrument Liabilities Not Carried At Fair Value	$ 78,159

[1] (1) Carrying values presented herein differ from those in the Company’s Statements of Financial Position because certain items within the respective financial statement captions are not considered financial instruments or out of scope under authoritative guidance relating to disclosures of the fair value of financial instruments. Financial statement captions excluded from the above table are not considered financial instruments.