Derivatives and Hedging Activity - Summary of Notional and Fair Values of Derivative Instruments (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Notional Amount	$ 218,700,000	$ 204,100,000
Derivatives Assets	10,300,000	13,500,000
Derivative Liabilities	2,900,000	17,500,000
Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	200,000,000	200,000,000
Derivatives Assets	2,200,000	11,400,000
Foreign Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	18,700,000	4,100,000
Derivatives Assets	8,100,000	2,100,000
Derivative Liabilities	$ 2,900,000	$ 17,500,000