Derivatives - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Risk participation Agreements [Line Items]
HedgedItemsOfCashFlowHedge	$ 200,000,000
Derivative Instruments Designated As Hedging Instruments Interest Income	381,000	0
Risk Participation Agreements Purchased [Domain]
Risk participation Agreements [Line Items]
Number of interest rate swaps	13
Risk Participation Agreements Sold [Domain]
Risk participation Agreements [Line Items]
Number of interest rate swaps	3
Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Notional Amount	200,000,000		100,000,000
Three Year Maturity [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Notional Amount	85,000,000
Four Year Maturity [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Notional Amount	$ 115,000,000