Investments (Allowance for Credit Losses and Recorded Investment in Commercial Mortgage and Other Loans) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Allowance for Credit Losses:
Ending Balance: Individually evaluated for impairment	$ 0	[1]	$ 0	[1]
Ending Balance: collectively evaluated for impairment	1,605	[2]	1,501	[2]
Total	1,605		1,501
Recorded Investment:
Ending balance gross of reserves: individually evaluated for impairment	0	[1],[3]	0	[1],[3]
Ending balance gross of reserves: collectively evaluated for impairment	464,993	[2],[3]	450,860	[2],[3]
Total	464,993	[3]	450,860	[3]
Agricultural Property Loans [Member]
Allowance for Credit Losses:
Ending Balance: collectively evaluated for impairment	200		200
Recorded Investment:
Ending balance gross of reserves: collectively evaluated for impairment	$ 54,100		$ 48,900

[1] There were no agricultural loans individually evaluated for impairments at June 30, 2012 and December 31, 2011.

[2] Agricultural loans collectively evaluated for impairment had a recorded investment of $54.1 million and $48.9 million and related allowance of $0.2 million and $0.2 million at June 30, 2012 and December 31, 2011, respectively.

[3] Recorded investment reflects the balance sheet carrying value gross of related allowance.