Derivatives and Hedging Activities - Fair Value of Derivative Financial Instruments and Classification on Balance Sheet (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value
Derivative Assets	$ 26,385	$ 6,896
Derivative Liabilities	8,204	22,445
Interest Rate Swaps Asset
Derivatives, Fair Value
Derivative Assets	26,280	6,896
Currency Forward Contracts
Derivatives, Fair Value
Derivative Assets	105	0
Derivative Liabilities	184	1,217
Interest Rate Swaps Liability
Derivatives, Fair Value
Derivative Liabilities	18,558	31,548
Futures Contracts
Derivatives, Fair Value
Derivative Assets	$ 1,612	$ 0