Derivative Financial Instruments - Effect of the Derivative Instruments on the Consolidated Statement of Income Derivative in Cash Flow Hedging Relationship (Detail) (Cash Flow Hedging [Member], Interest Rate Contracts One [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Cash Flow Hedging [Member] | Interest Rate Contracts One [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Comprehensive Income on Derivative (Effective Portion)	$ 25	$ (169)	$ 1,338	$ (588)