Fair Value of Derivative Financial Instruments and Their Classification on Balance Sheet (Detail) (Interest Rate Contract, USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Designated as Hedging Instrument | Other Assets
Derivatives, Fair Value [Line Items]
Asset derivatives	$ 206	$ 424
Designated as Hedging Instrument | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	3,617	2,305
Not Designated as Hedging Instrument | Other Assets
Derivatives, Fair Value [Line Items]
Asset derivatives	6,412	5,241
Not Designated as Hedging Instrument | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	$ 6,789	$ 5,492