Schedule of Location of Derivatives on Income Statement (Detail) (Interest Rate Contract, USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Interest Rate Contract
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative type for cash flow hedge	Interest Rate	Interest Rate	Interest Rate	Interest Rate
Amount of gain recognized in OCI on derivative (effective portion)	$ 57,294		$ 51,385
Amount of loss recognized in OCI on derivative (effective portion)		59,168		87,591
Location of loss reclassified from accumulated OCI into income (effective portion)	Interest Expense	Interest Expense	Interest Expense	Interest Expense
Amount of loss reclassified from accumulated OCI into income (effective portion)	30,585	28,352	60,515	56,164
Location of gain (loss)recognized in income on derivative (ineffective portion)	Interest Expense	Interest Expense	Interest Expense	Interest Expense
Amount of gain (loss) recognized in income on derivative (ineffective portion)	212		96
Amount of gain (loss) recognized in income on derivative (ineffective portion)		$ 169		$ 338