Consolidated Statements of Financial Position (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Cash and cash equivalents:
Cash and cash due from banks	$ 120,435	$ 121,294	$ 116,445
Interest-bearing deposits with unaffiliated banks and others	353,243	260,646	525,174
Total cash and cash equivalents	473,678	381,940	641,619
Investment securities:
Available-for-sale at fair value	676,007	667,276	585,992
Held-to-maturity (fair value - $192,372 at March 31, 2012, $183,769 at December 31, 2011 and $158,312 at March 31, 2011)	191,297	183,339	163,890
Total investment securities	867,304	850,615	749,882
Loans held for sale	25,080	18,818	4,033
Loans	3,843,098	3,831,285	3,682,516
Allowance for loan losses	(87,785)	(88,333)	(89,674)
Net loans	3,755,313	3,742,952	3,592,842
Premises and equipment (net of accumulated depreciation of $88,603 at March 31, 2012, $86,991 at December 31, 2011 and $82,676 at March 31, 2011)	66,661	65,997	65,135
Goodwill	113,414	113,414	113,414
Other intangible assets	10,939	11,472	13,060
Interest receivable and other assets	139,130	154,245	155,110
Total Assets	5,451,519	5,339,453	5,335,095
Deposits:
Noninterest-bearing	914,523	875,791	766,876
Interest-bearing	3,546,861	3,491,066	3,615,395
Total deposits	4,461,384	4,366,857	4,382,271
Interest payable and other liabilities	32,809	54,024	30,038
Short-term borrowings	335,082	303,786	286,193
Federal Home Loan Bank (FHLB) advances	42,120	43,057	72,854
Total liabilities	4,871,395	4,767,724	4,771,356
Shareholders' equity:
Preferred stock, no par value: Authorized - 200,000 shares, none issued
Common stock, $1 par value per share: Authorized - 45,000,000 shares at March 31, 2012 and December 31, 2011 and 30,000,000 at March 31, 2011; issued and outstanding - 27,491,026 shares at March 31, 2012, 27,456,907 at December 31, 2011 and 27,451,367 at March 31, 2011	27,491	27,457	27,451
Additional paid-in capital	431,549	431,277	429,990
Retained earnings	145,195	138,324	120,935
Accumulated other comprehensive loss	(24,111)	(25,329)	(14,637)
Total shareholders' equity	580,124	571,729	563,739
Total Liabilities and Shareholders' Equity	$ 5,451,519	$ 5,339,453	$ 5,335,095