Derivatives - Summary of (Losses) Gains on Derivatives Not Designated as Hedging Instruments (Detail) (Derivatives Not Designated as Hedging Instruments [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) Not Designated as Hedging Instruments [Line Items]
Net gain (loss) recognized in income	$ 70	$ (514)	$ (168)	$ 141