Derivative Financial Instruments - Schedule of Effect of Derivative Instruments on the Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ (284)	$ 292	$ (1,304)	$ 634
Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	(1,292)	(1,552)	(4,503)	(3,804)
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	81	81	243	248
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	(1,325)	(1,588)	(4,610)	(3,941)
Interest Rate Contracts [Member] | Interest Income / (Expense) [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	81	81	243	248
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	9	36	45	(48)
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	33	36	107	137
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	$ (293)	$ 256	(1,336)	$ 682
Foreign Currency Contracts [Member] | Other Income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative			$ (13)