Derivative Financial Instruments - Effect of the Derivative Instruments on the Consolidated Statement of Income Derivative in Fair Value Hedging Relationship (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative in Fair Value Hedging Relationship [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Location of (gain) loss recognized on derivative
Interest Income - Loans [Member] | Derivative in Fair Value Hedging Relationship [Member] | Interest Rate Contracts One [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Location of (gain) loss recognized on derivative	211	112	(1,635)	336
Interest Income - Loans [Member] | Derivative in Fair Value Hedging Relationship [Member] | Interest Rate Contracts Two [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Location of (gain) loss recognized on derivative	(211)	(112)	1,635	(336)
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]
Location of (gain) loss recognized on derivative	$ 169	$ 320	$ (239)	$ 600