Derivative Instruments - Effect of Corporation's Derivative Financial Instruments on Income Statement (Detail) (Interest Rate Contracts [Member], Other Income [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Interest Rate Contracts [Member] | Other Income [Member]
Derivative [Line Items]
Interest Rate Products	$ (39)	$ 167	$ (635)