Securities (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 987,560	$ 743,928
Gross Unrealized Gains	42,638	23,386
Gross Unrealized Losses	(2,088)	(3,448)
Fair Value	1,028,110	763,866
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Gross realized losses	250	148	10
Gross realized gains	384	206	1,100
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	678,631	491,530
Gross Unrealized Gains	19,323	16,139
Gross Unrealized Losses	(2,000)	(1,027)
Fair Value	695,954	506,642
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	263,075	249,117
Gross Unrealized Gains	22,746	7,247
Gross Unrealized Losses	(58)	(2,383)
Fair Value	285,763	253,981
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42,558
Gross Unrealized Gains	505
Gross Unrealized Losses	0
Fair Value	43,063
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,296	3,281
Gross Unrealized Gains	64	0
Gross Unrealized Losses	(30)	(38)
Fair Value	$ 3,330	$ 3,243

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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