Derivative Financial Instruments - Fair Value Derivatives Instruments (Detail) (Derivatives Not Designated as Hedging Instruments [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ 21,358	$ 23,966
Other Liabilities [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	21,358	23,966
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	21,358	23,966
Other Assets [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 21,358	$ 23,966