Securities Available-for-Sale (Details ) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	$ 1,208,527	$ 1,244,972
Gross Unrealized Gains	21,839	16,842
Gross Unrealized Losses	1,267	3,138
Total, fair value	1,229,099	1,258,676
U.S. Treasury [Member]
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	1,999	1,999
Gross Unrealized Gains	6	13
Total, fair value	2,005	2,012
U.S. Government Sponsored Enterprises [Member]
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	85,035	174,657
Gross Unrealized Gains	334	311
Gross Unrealized Losses		11
Total, fair value	85,369	174,957
Small Business Administration [Member]
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	8,142	8,714
Gross Unrealized Gains	113	87
Total, fair value	8,255	8,801
U.S. Government Agency and Sponsored Mortgage Backed Securities [Member]
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	1,041,144	1,020,752
Gross Unrealized Gains	21,187	16,262
Gross Unrealized Losses	250	1,176
Total, fair value	1,062,081	1,035,838
Privately Issued Residential Mortgage Backed Securities [Member]
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	3,072	3,509
Gross Unrealized Gains	32
Gross Unrealized Losses	21	311
Total, fair value	3,083	3,198
Obligations Issued by States and Political Subdivisions [Member]
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	66,377	21,515
Gross Unrealized Gains	52	84
Gross Unrealized Losses	960	957
Total, fair value	65,469	20,642
Other Debt Securities [Member]
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	2,300	13,293
Gross Unrealized Losses	36	683
Total, fair value	2,264	12,610
Equity Securities [Member]
Summary of Securities Available-for-Sale
Available-for-sale securities, amortized cost	458	533
Gross Unrealized Gains	115	85
Total, fair value	$ 573	$ 618

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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