Schedule of Location of Derivatives on Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Derivative [Line Items]
Interest rate hedge asset - Fair Value Asset Derivatives
Forward purchase commitment - Asset Derivatives found in Other Assets	5,452	6,327
Interest rate hedge liability - Fair Value Liability Derivatives	243,945	219,167
Forward purchase commitments found in Account payable and other liabilities