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Derivatives and Hedging Activity - Summary of Notional and Fair Values of Derivative Instruments (Detail) - USD ($)
Mar. 31, 2018
Dec. 31, 2017
Derivatives, Fair Value [Line Items]    
Notional Amount $ 313,500,000 $ 218,700,000
Derivatives Assets 15,800,000 10,300,000
Derivative Liabilities 2,000,000 2,900,000
Interest Rate Contracts [Member]    
Derivatives, Fair Value [Line Items]    
Notional Amount 275,000,000 200,000,000
Derivatives Assets 6,400,000 2,200,000
Foreign Exchange Contracts [Member]    
Derivatives, Fair Value [Line Items]    
Notional Amount 38,500,000 18,700,000
Derivatives Assets 9,400,000 8,100,000
Derivative Liabilities $ 2,000,000 $ 2,900,000