Schedule of Interest Rate Swap Agreements on Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Ending balance	$ (237,599)	$ (212,123)
Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Beginning balance	(218,451)	(47,676)
Unrealized loss on interest rate swaps	(141,392)	(273,389)
Reclassification of net losses included in income statement	116,792	102,614
Ending balance	$ (243,051)	$ (218,451)