Fair Value - Schedule of Financial Assets Measured at Fair Value on Nonrecurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Collateral dependent impaired loans	$ 75,576	$ 76,413
Other real estate owned	38,146	45,040
Total nonrecurring fair value measurements	113,722	121,453
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Collateral dependent impaired loans	42,504	72,694
Other real estate owned	0	0
Total nonrecurring fair value measurements	42,504	72,694
Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Collateral dependent impaired loans	33,072	3,719
Other real estate owned	38,146	45,040
Total nonrecurring fair value measurements	$ 71,218	$ 48,759