Gains (Losses) Related to Interest Rate Derivatives Designated as Hedges of Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative Instruments [Line Items]
Derivative instruments gain (loss) recognized in income, net	$ 682		$ 899
Derivative instruments gain (loss) recognized in expense, net	39	(453)	77	(1,034)
Derivatives Designated As Hedging Instruments [Member]
Derivative Instruments [Line Items]
Derivative instruments gain (loss) recognized in income, net	(57)	(706)	(178)	(764)
Derivative instruments gain (loss) recognized in expense, net	(33)	424	(60)	990
Designated as Hedging Instrument
Derivative Instruments [Line Items]
Derivative instruments gain (loss) recognized in income, net	$ 57	$ 706	$ 178	$ 764