Fair Value - Schedule of Financial Assets Measured at Fair Value on Nonrecurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Collateral-dependent impaired loans	$ 37,390	$ 72,694
Other real estate owned	21,452	43,803
Total nonrecurring fair value measurements	58,842	116,497
Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Collateral-dependent impaired loans
Other real estate owned
Total nonrecurring fair value measurements
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Collateral-dependent impaired loans	37,390	72,694
Other real estate owned
Total nonrecurring fair value measurements	37,390	72,694
Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned	21,452	43,803
Total nonrecurring fair value measurements	$ 21,452	$ 43,803