Fair Value, by Balance Sheet Grouping (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financial assets [Abstract]
Securities available for sale	$ 1,052,828	$ 908,718
Fair Value Measurements Using Level 1 [Member]
Financial assets [Abstract]
Cash and cash equivalents	442,644
Securities available for sale	10
Held to maturity securities	0
Net loans	0
Accrued interest receivable	0
Financial liabilities [Abstract]
Demand deposits	292,350
Interest bearing deposits	2,372,883
Short-term borrowings	0
Accrued interest payable	92
Fair Value Measurements Using Level 2 [Member]
Financial assets [Abstract]
Cash and cash equivalents	0
Securities available for sale	1,052,818
Held to maturity securities	165,297
Net loans	0
Accrued interest receivable	4,805
Financial liabilities [Abstract]
Demand deposits	0
Interest bearing deposits	1,113,316
Short-term borrowings	161,751
Accrued interest payable	375
Fair Value Measurements Using Level 3 [Member]
Financial assets [Abstract]
Cash and cash equivalents	0
Securities available for sale	0
Held to maturity securities	0
Net loans	2,671,545
Accrued interest receivable	7,898
Financial liabilities [Abstract]
Demand deposits	0
Interest bearing deposits	0
Short-term borrowings	0
Accrued interest payable	0
Carrying Value [Member]
Financial assets [Abstract]
Cash and cash equivalents	442,644	532,943
Securities available for sale	1,052,828	908,718
Held to maturity securities	155,951	216,288
Federal Reserve Bank and Federal Home Loan Bank stock	9,632	9,004
Net loans	2,558,577	2,472,586
Accrued interest receivable	12,703	13,952
Financial liabilities [Abstract]
Demand deposits	292,350	267,776
Interest bearing deposits	3,484,103	3,468,197
Short-term borrowings	161,751	147,563
Accrued interest payable	467	762
Fair Value [Member]
Financial assets [Abstract]
Cash and cash equivalents	442,644	532,943
Securities available for sale	1,052,828	908,718
Held to maturity securities	165,297	224,440
Net loans	2,671,545	2,590,803
Accrued interest receivable	12,703	13,952
Financial liabilities [Abstract]
Demand deposits	292,350	267,776
Interest bearing deposits	3,486,199	3,474,558
Short-term borrowings	161,751	147,563
Accrued interest payable	$ 467	$ 762

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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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