Derivatives - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) Derivatives	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Derivatives	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Risk participation Agreements [Line Items]
HedgedItemsOfCashFlowHedge	$ 115,000		$ 115,000
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ (653)	$ 0
Risk Participation Agreements Purchased [Domain]
Risk participation Agreements [Line Items]
Number of interest rate swaps | Derivatives	36		36
Risk Participation Agreements Sold [Domain]
Risk participation Agreements [Line Items]
Number of interest rate swaps | Derivatives	13		13
Forward Contracts [Member]
Risk participation Agreements [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ 33	(17)	$ (29)	$ 95
Derivative Liability, Cost Basis, Gross Asset	6,400		6,400		$ 14,300
Derivative Liability, Fair Value, Gross Asset	7,200		7,200		14,700
Derivative Liability, Notional Amount, Gross Asset	19,800		19,800		13,800
Forward Contracts [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Fair Value, Net	(48)		(48)		(19)
Derivative, Notional Amount	20,000		20,000		17,000
Interest Rate Contract [Member]
Risk participation Agreements [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)			(653)	0
Foreign Exchange [Member]
Risk participation Agreements [Line Items]
Derivative, Net Hedge Ineffectiveness Gain (Loss)	11	(1)	8	1
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Fair Value, Net	23		23		70
Derivative, Notional Amount	3,222		3,222		10,077
Derivative Liability, Cost Basis, Gross Asset	3,200		3,200		10,000
Derivative Liability, Fair Value, Gross Asset	3,200		3,200		10,100
Interest Rate Swap [Member]
Risk participation Agreements [Line Items]
Derivative Instruments Designated As Hedging Instruments Interest Income	(150)	136	(231)	385
Derivative, Net Hedge Ineffectiveness Gain (Loss)	10	$ (5)	10	$ 73
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Risk participation Agreements [Line Items]
Derivative, Fair Value, Net	(492)		(492)		(459)
Derivative, Notional Amount	$ 115,000		$ 115,000		$ 150,000