Derivatives and Hedging Activities - Summary of Cash Flow Hedges (Detail) - Cash flow hedges [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Notional Amount, Derivative assets	$ 521,072	$ 72,262
Notional Amount, Derivative liabilities	213,800	440,637
Notional Amount, Total	734,872	512,899
Fair Value, Derivative assets	25,445	2,379
Fair Value, Derivative liabilities	(8,505)	(29,777)
Fair Value, Total	16,940	(27,398)
Accumulated Other Comprehensive Income (Loss) [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Derivative assets	21,611	2,055
Fair Value, Derivative liabilities	(12,277)	(34,311)
Fair Value, Total	9,334	(32,256)
Net gain (loss) to be reclassified within 12 months	$ 400	$ (26,700)