Fair Value - Quantitative Information About Level 3 Fair Value Measurements (Detail) - Pooled Trust Preferred [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 1,702	$ 3,413
Collateral Default Rate [Member] \| Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input utilized two	0.5% in 2016 and thereafter	1% in 2015; 0.5% in 2016 and thereafter
Yield (Weighted Average) [Member] \| Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input utilized one	10.00%	9.00%
Prepayment Speed [Member] \| Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input utilized two	2.0% constant prepayment rate in 2016 and thereafter	2.0% constant prepayment rate in 2015 and thereafter

0.5% in 2016 and thereafter

1% in 2015; 0.5% in 2016 and thereafter

2.0% constant prepayment rate in 2016 and thereafter

2.0% constant prepayment rate in 2015 and thereafter