Derivative Instruments and Hedging Activities - Schedule of Gross Amounts of Derivative Assets and Derivative Liabilities (Detail) (Not Designated as Hedging Instruments [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Not Designated as Hedging Instruments [Member]
Derivative Asset [Abstract]
Gross amounts recognized	$ 12,341		$ 14,012
Gross amounts offset	(216)		(314)
Net amounts presented in the Consolidated Balance Sheets	12,125		13,698
Gross amounts not offset	0	[1]	0	[1]
Net Amount	12,125		13,698
Derivative Liability [Abstract]
Gross amounts recognized	12,319		13,961
Gross amounts offset	(216)		(314)
Net amounts presented in the Consolidated Balance Sheets	12,103		13,647
Gross amounts not offset	(11,492)	[1]	(12,611)	[1]
Net Amount	$ 611		$ 1,036

[1] Amounts represent posted collateral.