Fair Values of Derivative Instruments on Condensed Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 402	$ 975
Derivative financial instruments, Liability	27,648	33,095
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	10	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	402	975
Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Derivative financial instruments, Liability	27,648	33,095
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	10
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Liability at Fair Value	$ 0	$ 0