Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Available-for-sale Securities
Amortized Cost	$ 1,155,383	$ 1,140,212
Gross Unrealized Gains	35,237	35,050
Gross Unrealized Losses	(31,418)	(32,486)
Estimated fair Value of Available for Sale	1,159,202	1,142,776
Equity Securities [Member]
Available-for-sale Securities
Amortized Cost	1,860	1,860
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated fair Value of Available for Sale	1,860	1,860
Debt Securities [Member]
Available-for-sale Securities
Amortized Cost	1,153,523	1,138,352
Gross Unrealized Gains	35,237	35,050
Gross Unrealized Losses	(31,418)	(32,486)
Estimated fair Value of Available for Sale	1,157,342	1,140,916
Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage Backed Securities - Commercial [Member]
Available-for-sale Securities
Amortized Cost	175	193
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	(1)
Estimated fair Value of Available for Sale	177	193
Obligations of U.S. Government-Sponsored Enterprises [Member] \| Mortgage Backed Securities - Residential [Member]
Available-for-sale Securities
Amortized Cost	815,982	771,196
Gross Unrealized Gains	29,853	29,835
Gross Unrealized Losses	(96)	0
Estimated fair Value of Available for Sale	845,739	801,031
Obligations of U.S. Government-Sponsored Enterprises [Member] \| Other Government Sponsored Enterprises [Member]
Available-for-sale Securities
Amortized Cost	241,697	267,807
Gross Unrealized Gains	870	973
Gross Unrealized Losses	(1)	(132)
Estimated fair Value of Available for Sale	242,566	268,648
Obligations of States and Political Subdivisions [Member]
Available-for-sale Securities
Amortized Cost	443	444
Gross Unrealized Gains	6	15
Gross Unrealized Losses	0	0
Estimated fair Value of Available for Sale	449	459
Pooled Trust Preferred Collateralized Debt Obligations [Member]
Available-for-sale Securities
Amortized Cost	52,889	54,762
Gross Unrealized Gains	153	3
Gross Unrealized Losses	(31,250)	(31,785)
Estimated fair Value of Available for Sale	21,792	22,980
Obligations of U.S. Government Agencies [Member] \| Mortgage Backed Securities - Residential [Member]
Available-for-sale Securities
Amortized Cost	30,541	32,139
Gross Unrealized Gains	4,079	4,061
Gross Unrealized Losses	0	(6)
Estimated fair Value of Available for Sale	34,620	36,194
Corporate Securities [Member]
Available-for-sale Securities
Amortized Cost	11,796	11,811
Gross Unrealized Gains	274	162
Gross Unrealized Losses	(71)	(562)
Estimated fair Value of Available for Sale	$ 11,999	$ 11,411

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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