Derivatives - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) Derivatives	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Derivatives	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Risk participation Agreements [Line Items]
HedgedItemsOfCashFlowHedge	$ 200,000		$ 200,000
Derivative Instruments Designated As Hedging Instruments Interest Income	$ 565	$ 29	$ 1,503	$ 29
Risk Participation Agreements Purchased [Domain]
Risk participation Agreements [Line Items]
Number of interest rate swaps | Derivatives	15		15
Risk Participation Agreements Sold [Domain]
Risk participation Agreements [Line Items]
Number of interest rate swaps | Derivatives	3		3
Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Notional Amount	$ 200,000		$ 200,000		$ 100,000
Three Year Maturity [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Notional Amount	85,000		85,000
Four Year Maturity [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Notional Amount	$ 115,000		$ 115,000