Derivatives and Hedging Activities - Summary of Cash Flow Hedges (Detail) - Cash flow hedges - USD ($)	Sep. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Notional amount, derivative assets	$ 388,269,000	$ 367,330,000
Derivative liabilities	167,706,000	47,447,000
Notional amount, total	555,975,000	414,777,000
Fair value, derivative assets	25,353,000	16,027,000
Fair value, derivative liabilities	(3,750,000)	(813,000)
Fair value, total	21,603,000	15,214,000
Unrealized gain on cash flow hedges
Derivatives, Fair Value [Line Items]
Fair value, derivative assets	53,713,000	34,578,000
Fair value, derivative liabilities	(33,791,000)	(19,709,000)
Fair value, total	19,922,000	14,869,000
Net gain to be reclassified within 12 months	$ 13,994	$ 12,940