Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Assets:
Cash and cash equivalents	$ 241,823	$ 381,940	$ 400,279	$ 536,165
Investment securities:
Loans held-for-sale	12,625	18,818	6,874
Net loans	3,875,631	3,742,952	3,658,277
Liabilities:
FHLB advances	38,177	43,057	71,928
Carrying Amount [Member]
Investment securities:
Available-for-sale	4,755
Nonmarketable equity securities	25,572	25,572	25,572
Carrying Amount [Member] \| Level 1[Member]
Assets:
Cash and cash equivalents	241,823	381,940	400,279
Carrying Amount [Member] \| Level 2 [Member]
Investment securities:
Available-for-sale	675,476	667,276	612,466
Held-to-maturity	205,034	175,339	182,029
Loans held-for-sale	12,625	18,818	6,874
Interest receivable	15,764	16,308	15,621
Liabilities:
Deposits without defined maturities	2,933,079	2,851,883	2,678,064
Interest payable	1,755	2,147	2,487
Short-term borrowings	299,748	303,786	276,600
FHLB advances	38,177	43,057	71,928
Carrying Amount [Member] \| Level 3 [Member]
Investment securities:
Held-to-maturity	8,000	8,000	8,000
Net loans	3,875,631	3,742,952	3,658,277
Liabilities:
Time deposits	1,450,465	1,514,974	1,572,912
Fair Value [Member]
Investment securities:
Available-for-sale	4,755
Nonmarketable equity securities	25,572	25,572	25,572
Fair Value [Member] \| Level 1[Member]
Assets:
Cash and cash equivalents	241,823	381,940	400,279
Fair Value [Member] \| Level 2 [Member]
Investment securities:
Available-for-sale	675,476	667,276	612,466
Held-to-maturity	205,852	175,769	179,595
Loans held-for-sale	12,625	18,972	6,874
Interest receivable	15,764	16,308	15,621
Liabilities:
Deposits without defined maturities	2,933,079	2,851,883	2,678,064
Interest payable	1,755	2,147	2,487
Short-term borrowings	299,748	303,786	276,600
FHLB advances	39,066	44,307	73,380
Fair Value [Member] \| Level 3 [Member]
Investment securities:
Held-to-maturity	8,000	8,000	8,000
Net loans	3,886,308	3,753,799	3,651,307
Liabilities:
Time deposits	$ 1,469,738	$ 1,538,566	$ 1,596,321

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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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Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.

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