Investments (Mortgage Loans by Method of Evaluation and Related Valuation Allowances) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Mortgage Loans:
Total mortgage loans	$ 2,496,251	$ 2,312,167
Mortgage Loans Net Of Valuation Allowances [Abstract]
Mortgage loans on real estate (net of valuation allowances)	2,488,582	2,300,587
Commercial Real Estate Portfolio Segment
Mortgage Loans:
Evaluated individually for credit losses	32,624	39,956
Evaluated collectively for credit losses	2,463,627	2,272,211
Total mortgage loans	2,496,251	2,312,167
Valuation Allowances:
Specific for credit losses	4,691	6,980
Non-specifically identified credit losses	2,978	4,600
Total valuation allowances	$ 7,669	$ 11,580

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

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