Fair Value - Securities Available for Sale Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) - Pooled Trust Preferred [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,160	$ 798	$ 905	$ 661
Total gains or (losses):
Included in other comprehensive income (unrealized)	0	73	255	210
Ending Balance	$ 1,160	$ 871	$ 1,160	$ 871