Investment Securities Available for Sale (Amortized Cost and Estimated Market Value of Investment Securities Available for Sale) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 220,013	$ 179,879
Gross Unrealized Gains	1,711	1,036
Gross Unrealized Losses	(13,388)	(15,636)
Estimated Market Value	208,336	165,279
U.S. agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	138,416	102,059
Gross Unrealized Gains	1,019	760
Gross Unrealized Losses		(43)
Estimated Market Value	139,435	102,776
State and municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,605	18,526
Gross Unrealized Gains	12	26
Gross Unrealized Losses	(31)	(8)
Estimated Market Value	21,586	18,544
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	55,000	55,000
Gross Unrealized Losses	(13,286)	(15,551)
Estimated Market Value	41,714	39,449
Equity investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,992	4,294
Gross Unrealized Gains	680	250
Gross Unrealized Losses	(71)	(34)
Estimated Market Value	$ 5,601	$ 4,510

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

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

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Reference 10: http://www.xbrl.org/2003/role/presentationRef

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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