Securities - Amortized Cost and Estimated Fair Value of Investment Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 336,710	$ 330,060
Gross Unrealized Gains	11,166	10,551
Gross Unrealized Losses	(967)	(644)
Fair Value	346,909	339,967
U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,605	14,670
Gross Unrealized Gains	271	267
Gross Unrealized Losses	(6)
Fair Value	6,870	14,937
State, county and municipal securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	109,736	75,665
Gross Unrealized Gains	4,864	3,558
Gross Unrealized Losses	(210)	(90)
Fair Value	114,390	79,133
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,545	11,640
Gross Unrealized Gains	330	167
Gross Unrealized Losses	(547)	(406)
Fair Value	10,328	11,401
Mortgage backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	209,824	228,085
Gross Unrealized Gains	5,701	6,559
Gross Unrealized Losses	(204)	(148)
Fair Value	$ 215,321	$ 234,496

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details