Assets Measured at Fair Value on Non-Recurring Basis (Detail) - Fair Value, Measurements, Non-Recurring [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 24,413	$ 5,330
Total Gains (Losses) Recognized	(942)	2,345
Impaired loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	21,893	5,122
Total Gains (Losses) Recognized	(933)	2,345
Other real estate owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	2,520	208
Total Gains (Losses) Recognized	(9)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	24,413	5,330
Significant Unobservable Inputs (Level 3) [Member] | Impaired loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	21,893	5,122
Significant Unobservable Inputs (Level 3) [Member] | Other real estate owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 2,520	$ 208