Derivative Financial Instruments - Effect of Derivative Instruments on Consolidated Statement of Income Derivative in Fair Value Hedging Relationship (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
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	$ 1,478	$ 719
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	(1,478)	(719)
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	$ 2	$ 189