Securities (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 961,296	$ 987,560
Gross Unrealized Gains	39,526	42,638
Gross Unrealized Losses	(1,609)	(2,088)
Fair Value	999,213	1,028,110
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	652,263	678,631
Gross Unrealized Gains	18,650	19,323
Gross Unrealized Losses	(1,329)	(2,000)
Fair Value	669,584	695,954
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	263,298	263,075
Gross Unrealized Gains	20,466	22,746
Gross Unrealized Losses	(212)	(58)
Fair Value	283,552	285,763
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42,439	42,558
Gross Unrealized Gains	350	505
Gross Unrealized Losses	(37)	0
Fair Value	42,752	43,063
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,296	3,296
Gross Unrealized Gains	60	64
Gross Unrealized Losses	(31)	(30)
Fair Value	$ 3,325	$ 3,330

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.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- 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.

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