Fair Value - Quantitative Information About Level 3 Fair Value Measurements (Detail) (Pooled Trust Preferred [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	905	661
Collateral Default Rate [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input utilized two	1% in 2015; 0.5% in 2016 and thereafter	2% in 2014; 1.5% in 2015; 1.0% in 2016; 0.5% in 2017 and thereafter
Yield [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input utilized one	11.00%	15.00%
Prepayment Speed [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input utilized two	2.0% constant prepayment rate in 2015 and thereafter	2.0% constant prepayment rate in 2014 and thereafter