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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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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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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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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 tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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Federal Income Taxes (Effective Tax Rate Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate, Tax Rate Reconciliation [Abstract]
Tax at statutory rate									$ 31,367	$ 28,388	$ 25,133
Tax-exempt interest income									(3,118)	(2,746)	(2,524)
Income tax credits									(1,624)	(1,615)	(1,561)
Other, net									875	273	(248)
Provision for federal income taxes	$ 7,050us-gaap_IncomeTaxExpenseBenefit	$ 7,450us-gaap_IncomeTaxExpenseBenefit	$ 7,100us-gaap_IncomeTaxExpenseBenefit	$ 5,900us-gaap_IncomeTaxExpenseBenefit	$ 6,100us-gaap_IncomeTaxExpenseBenefit	$ 6,400us-gaap_IncomeTaxExpenseBenefit	$ 6,100us-gaap_IncomeTaxExpenseBenefit	$ 5,700us-gaap_IncomeTaxExpenseBenefit	$ 27,500us-gaap_IncomeTaxExpenseBenefit	$ 24,300us-gaap_IncomeTaxExpenseBenefit	$ 20,800us-gaap_IncomeTaxExpenseBenefit
Effective federal income tax rate									30.70%	30.00%	29.00%