Fair Value - Quantitative Information About Level 3 Fair Value Measurements (Detail) - Pooled Trust Preferred [Member] - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 1,160	$ 905
Collateral Default Rate [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input utilized two	0.71% and declining to 0.5% over the remainder of 2015 and thereafter	1% in 2015; 0.5% in 2016 and thereafter
Yield [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input utilized one	9.00%	11.00%
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 2015 and thereafter