Income Taxes (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Expected federal tax on income	$ 51,140	$ 53,923	$ 52,210
Add (deduct) tax effects of:
Tax-exempt interest	(6,849)	(6,829)	(6,836)
Dividend received deduction	(3,566)	(3,382)	(2,132)
Other, net	1,145	(539)	2,065
Income tax expense provided on income	$ 41,870us-gaap_IncomeTaxExpenseBenefit	$ 43,173us-gaap_IncomeTaxExpenseBenefit	$ 45,307us-gaap_IncomeTaxExpenseBenefit

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for dividend.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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