Derivatives and Hedging Activities - Summary of Cash Flow Hedge Instruments (Detail) - Cash flow hedge instruments - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Notional amount, derivative assets	$ 72,262	$ 545,638
Notional amount, derivative liabilities	440,637	42,207
Notional amount, total	512,899	587,845
Fair value, derivative assets	2,379	44,570
Fair value, derivative liabilities	(29,777)	(1,815)
Fair value, total	(27,398)	42,755
Accumulated Other Comprehensive Income (Loss) (2)(3)
Derivatives, Fair Value [Line Items]
Fair value, derivative assets	2,055	42,634
Fair value, derivative liabilities	(34,311)	(1,453)
Fair value, total	(32,256)	41,181
Net gain (loss) related to cash flow hedges recorded in accumulated other comprehensive income (loss) that is expected to be recognized in next 12 months	$ (26,700)	$ 31,900