Income Taxes - Summary of Reasons for Differences Between Statutory Federal Income Tax Rates and Effective Tax Rates (Detail)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Statutory Federal Tax Rate [Line Items]
Statutory rate	34.00%	34.00%
Increase (decrease) resulting from:
Tax exempt interest	(8.30%)	(8.50%)
Bank owned life insurance	(3.10%)	(2.70%)
Other, net	0.70%	1.80%
Effective Income Tax Rate, Total	23.30%	24.60%

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

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

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Percentage 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 life insurance expense.

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