Fair Value of Financial Instrument - Summary of Fair Value Measurements of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	$ 395,695	$ 339,967
Total recurring liabilities at fair value	2,978	2,049
Us Government Sponsored Agencies [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	6,870
State, county and municipal securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	114,390	79,133
Corporate debt securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	10,328	11,401
Mortgage backed securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	215,321	234,496
Mortgage loans held for sale [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	48,786
Derivative Financial Instruments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	2,978	2,049
Us Government Sponsored Agencies [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value		14,937
Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	28,747	6,268
Level 1 [Member] | State, county and municipal securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	4,854	2,966
Level 1 [Member] | Mortgage backed securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	23,893	3,302
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	364,948	331,699
Total recurring liabilities at fair value	2,978	2,049
Level 2 [Member] | Us Government Sponsored Agencies [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	6,870
Level 2 [Member] | State, county and municipal securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	109,536	76,167
Level 2 [Member] | Corporate debt securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	8,328	9,401
Level 2 [Member] | Mortgage backed securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	191,428	231,194
Level 2 [Member] | Mortgage loans held for sale [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	48,786
Level 2 [Member] | Derivative Financial Instruments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	2,978	2,049
Level 2 [Member] | Us Government Sponsored Agencies [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value		14,937
Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	2,000	2,000
Level 3 [Member] | Corporate debt securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Recurring assets at fair value	$ 2,000	$ 2,000