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	Mar. 31, 2015		Dec. 31, 2014
Not Designated as Hedging Instruments [Member]
Derivative Asset [Abstract]
Gross amounts recognized	$ 14,020		$ 13,203
Gross amounts offset	0		(222)
Net amounts presented in the Consolidated Balance Sheets	14,020		12,981
Gross amounts not offset	0	[1]	0	[1]
Net Amount	14,020		12,981
Derivative Liability [Abstract]
Gross amounts recognized	13,979		13,175
Gross amounts offset	0		(222)
Net amounts presented in the Consolidated Balance Sheets	13,979		12,953
Gross amounts not offset	(12,498)	[1]	(12,059)	[1]
Net Amount	$ 1,481		$ 894

[1] Amounts represent posted collateral.