Taxes On Income (Reconciliation from the Expected Tax Expense (Benefit) Using the U.S. Federal Income Tax Rate) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Taxes On Income [Abstract]
Computed tax (benefit) expense at statutory rates	$ 11,777	$ 9,867	$ 9,124
Increase (decrease) in income taxes results from:
Benefit of income not subject to U.S. Federal income tax	(209)	(213)	(213)
Expenses not deductible for U.S. Federal income tax	129	96	150
State income taxes, net of Federal income tax benefit	907	749	476
Texas tax refund (federally tax affected)			50oksb_TexasTaxRefundFederallyTaxAffected
Other	13	181	296
Income Tax Expense (Benefit), Total	12,617us-gaap_IncomeTaxExpenseBenefit	10,756us-gaap_IncomeTaxExpenseBenefit	9,883us-gaap_IncomeTaxExpenseBenefit
Tax Credit Recapture		$ 76

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Texas Tax Refund (Federally Tax Affected) resulting in a difference between the expected tax rate and teh effective tax rate.

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

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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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