Disclosures about Fair Value of Assets and Liabilities - Reconciliation of the Beginning and Ending Balances of Recurring Fair Value Measurements Recognized in the Accompanying Condensed Consolidated Balance Sheet Using Significant Unobservable (Level 3) Inputs (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Hedged Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Beginning balance	$ 54,362
Included in net income	(74)
Purchases, issuances, and settlements	6,114
Principal payments	(491)
Transfers out to Level 2	(59,911)
Ending balance
Forward Sale Commitments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Beginning balance	662
Included in net income	(152)
Transfers out to Level 2	(510)
Ending balance
Interest Rate Swap Agreements [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Beginning balance	(7,101)
Included in net income	74
Included in other comprehensive income, gross	563
Transfers out to Level 2	6,464
Ending balance
Commitments to Originate Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Included in net income	(71)
Transfers out to Level 2	71
Ending balance