Fair Value Disclosures (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair value disclosure
Cost	$ 3,612,636us-gaap_AvailableForSaleSecurities
Other intangible assets	14,760	16,548
Non-recurring basis
Fair value disclosure
Goodwill	0	0	0
Other intangible assets	0	0	0
Single broker quotes \| Level 3
Fair value disclosure
Cost	12,029	13,821
Independent and non-binding broker quotes \| Level 3
Fair value disclosure
Cost	$ 11,198	$ 11,934

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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