Fair Values of Derivative Instruments on Condensed Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 275	$ 975
Derivative financial instruments, Liability	25,816	33,095
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	52	43
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Liability at Fair Value	0	0
Other assets
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	275	975
Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Derivative financial instruments, Liability	25,816	33,095
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	52	43
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Liability at Fair Value	$ 0	$ 0