Disclosures about Fair Value of Assets an Liabilities - Schedule of Fair Value Transfer Among Levels (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Reason for Transfer (a)	Valuation determined by widely accepted techniques including discounted cash flow analysis on expected cash flows of each derivative and observable market rate inputs such as yield curves and contractual terms on each instrument.
Reason for Transfer (b)	Valuation determined by quoted prices for similar loans in the secondary market with an expected fallout rate (interest rate locked pipeline loans not expected to close). Fallout rate is not considered a significant input to the fair value in its entirety.
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	53,886
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Hedged Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	(59,911)
Hedged Loans [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Hedged Loans [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	59,911
Hedged Loans [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Forward Sale Commitments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	(510)
Forward Sale Commitments [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Forward Sale Commitments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	510
Forward Sale Commitments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Interest Rate Swap Agreements [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	6,464
Interest Rate Swap Agreements [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Interest Rate Swap Agreements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	(6,464)
Interest Rate Swap Agreements [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Commitments to Originate Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	71
Commitments to Originate Loans [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3
Commitments to Originate Loans [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3	(71)
Commitments to Originate Loans [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Transfers out to Level 1, 2, and 3