Derivative Financial Instruments - Effect of Derivative Instruments on Consolidated Statement of Income Derivative in Fair Value Hedging Relationship (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest Income - Loans [Member] | Derivative in Fair Value Hedging Relationship [Member] | Interest Rate Contracts One [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized on Derivative	$ 574	$ 1,261	$ (2,267)
Interest Income - Loans [Member] | Derivative in Fair Value Hedging Relationship [Member] | Interest Rate Contracts Two [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized on Derivative	(574)	(1,261)	2,267
Derivatives Not Designated as Hedging Instruments [Member] | Other income - Gain on Sale of Loans [Member] | Mortgage Loan Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized on Derivative	$ 195	$ 256	$ (667)