Effects of Cash Flow Hedge Derivative Instruments on the Accompanying Condensed Consolidated Statements of Comprehensive Income (Detail) (Interest Rate Swap [Member], Cash Flow Hedge [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Interest Rate Swap [Member] | Cash Flow Hedge [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Loss reclassified from AOCI (effective portion)	$ (1,615)	$ (1,499)	$ (4,755)	$ (10,131)