Impact on Interest Expense of Interest Rate Agreements Accounted for as Cash Flow Hedges (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative [Line Items]
Total interest expense	$ (21,833)	$ (28,285)	$ (61,651)	$ (87,822)
Cash Flow Hedging | Interest Rate Contract
Derivative [Line Items]
Net interest expense on cash flow interest rate agreements	(1,474)	(1,409)	(4,406)	(4,361)
Realized expense due to ineffective portion of hedges				(34)
Realized net losses reclassified from other comprehensive income	(62)	(1,126)	(219)	(3,260)
Total interest expense	$ (1,536)	$ (2,535)	$ (4,625)	$ (7,655)