Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets:
Securities	$ 587,602	$ 516,844
Loans Held-for-Sale	16,641	21,485
Derivative Assets	187	0
Derivative Liabilities	178	0
Significant Unobservable Inputs (Level 3) [Member]
Assets:
Securities	12,500
Fair Value, Measurements, Recurring [Member] | U.S. Treasury and Agency Securities [Member]
Assets:
Securities	23,472	6,422
Fair Value, Measurements, Recurring [Member] | Corporate Securities [Member]
Assets:
Securities	0	1,005
Fair Value, Measurements, Recurring [Member] | Obligations of State and Political Subdivisions [Member]
Assets:
Securities	76,485	64,799
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities - Residential [Member]
Assets:
Securities	486,912	443,934
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Assets:
Securities	733	684
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Securities	380	331
Loans Held-for-Sale	0	0
Derivative Assets	0	0
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury and Agency Securities [Member]
Assets:
Securities	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Securities [Member]
Assets:
Securities	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Obligations of State and Political Subdivisions [Member]
Assets:
Securities	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage-backed Securities - Residential [Member]
Assets:
Securities	0	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member]
Assets:
Securities	380	331
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Securities	574,700	511,080
Loans Held-for-Sale	16,641	21,485
Derivative Assets	187	0
Derivative Liabilities	178	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury and Agency Securities [Member]
Assets:
Securities	23,472	6,422
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Securities [Member]
Assets:
Securities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Obligations of State and Political Subdivisions [Member]
Assets:
Securities	64,316	60,724
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mortgage-backed Securities - Residential [Member]
Assets:
Securities	486,912	443,934
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Equity Securities [Member]
Assets:
Securities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets:
Securities	12,522	5,433
Loans Held-for-Sale	0	0
Derivative Assets	0	0
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury and Agency Securities [Member]
Assets:
Securities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate Securities [Member]
Assets:
Securities	0	1,005
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Obligations of State and Political Subdivisions [Member]
Assets:
Securities	12,169	4,075
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mortgage-backed Securities - Residential [Member]
Assets:
Securities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member]
Assets:
Securities	$ 353	$ 353