Securities (Summary of Amortized Costs and Estimated Fair Values of Available-For-Sale Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	$ 761,138	$ 572,917
Available-for-sale, Unrealized Gains	20,808	20,225
Available-for-sale, Unrealized Losses	(896)	(3,106)
Available-for-sale, Fair Value	781,050	590,036
Obligations of states and political subdivisions [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	31,112	37,138
Available-for-sale, Unrealized Gains	1,928	2,620
Available-for-sale, Unrealized Losses
Available-for-sale, Fair Value	33,040	39,758
Mortgage-backed securities issued or guaranteed by U.S. government sponsored enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	345,528	361,073
Available-for-sale, Unrealized Gains	12,699	15,861
Available-for-sale, Unrealized Losses	(79)
Available-for-sale, Fair Value	358,148	376,934
Collateralized mortgage obligations issued or guaranteed by U.S. government sponsored enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	375,627	127,153
Available-for-sale, Unrealized Gains	6,181	1,628
Available-for-sale, Unrealized Losses	(120)	(331)
Available-for-sale, Fair Value	381,688	128,450
Private issue collateralized mortgage obligations [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost	8,871	12,557
Available-for-sale, Unrealized Gains
Available-for-sale, Unrealized Losses	(697)	(1,916)
Available-for-sale, Fair Value	8,174	10,641
Obligations of U.S. government sponsored enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost		29,996
Available-for-sale, Unrealized Gains		116
Available-for-sale, Unrealized Losses		(5)
Available-for-sale, Fair Value		30,107
Total debt securities
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost		567,917
Available-for-sale, Unrealized Gains		20,225
Available-for-sale, Unrealized Losses		(2,252)
Available-for-sale, Fair Value		585,890
Equity securities [Member]
Schedule of Investments [Line Items]
Available-for-sale, Amortized Cost		5,000
Available-for-sale, Unrealized Gains
Available-for-sale, Unrealized Losses		(854)
Available-for-sale, Fair Value		$ 4,146

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 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