Derivative Financial Instruments - Schedule of Effect of Derivative Instruments on the Consolidated Statements of Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ 788	$ 153
Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	82	465
Interest Rate Contracts [Member] | Interest Income / (Expense) [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	23	359
Interest Rate Contracts [Member] | Other Income / (Expense) [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative		73
Interest Rate Contracts [Member] | Other Income / (Expense) [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	59	106
Mortgage Contracts [Member] | Mortgage Banking Revenue [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ 788	$ 80