Investments (Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Loans originated during the year	$ 37,100,000	$ 34,100,000
Recognized valuation losses	0us-gaap_ProvisionForLoanAndLeaseLosses	0us-gaap_ProvisionForLoanAndLeaseLosses	700,000us-gaap_ProvisionForLoanAndLeaseLosses
Real estate investments	28,774,000us-gaap_OtherLongTermInvestments	30,991,000us-gaap_OtherLongTermInvestments
Realized gains (losses) on investments	11,605,000us-gaap_RealizedInvestmentGainsLosses	8,653,000us-gaap_RealizedInvestmentGainsLosses	13,200,000us-gaap_RealizedInvestmentGainsLosses
Debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Realized gains (losses) on investments	11,800,000	9,000,000	14,500,000
Held-to-maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Realized loss on a security sold			300,000
Real Estate [Member]
Schedule of Available-for-sale Securities [Line Items]
Real estate investments	16,700,000	18,200,000
Operating income recognized on real estate investment properties	1,700,000	1,700,000	1,600,000
Realized gains (losses) on investments	1,000,000	300,000	2,600,000
Other-than Temporary Impairment Write-down on Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Realized gains (losses) on investments	200,000
External Credit Rating, Non Investment Grade [Member] \| Debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt securities below investment grade	$ 147,100,000	$ 178,600,000
Debt securities below investment grade, percentage of total invested assets	1.50%	1.90%

Available-for-sale Securities and Held-to-maturity Securities, Percentage of Total Invested Assets

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Amount of debt and equity financial instruments classified as either held-to-maturity or available-for-sale.

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This item represents the gain (loss) realized on the sale of held-to-maturity securities disposed of during the period. Additionally, this item may include, if not separately presented, any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt securities which are being or have been recognized in earnings during the period.

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Total amount of additions to mortgage loans other than new loans during the reporting period.

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Other long-term investments not otherwise specified in the taxonomy, not including investments in marketable securities.

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The total amount of other operating income, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operation.

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Amount of expense related to estimated loss from loan and lease transactions.

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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