Consolidated Statements of Financial Position (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Cash and cash equivalents:
Cash and cash due from banks	$ 122,010	$ 121,294	$ 129,209
Interest-bearing deposits with unaffiliated banks and others	119,813	260,646	271,070
Total cash and cash equivalents	241,823	381,940	400,279
Investment securities:
Available-for-sale at fair value	680,231	667,276	612,466
Held-to-maturity (fair value $213,852 at June 30, 2012, $183,769 at December 31, 2011 and $187,595 at June 30, 2011)	213,034	183,339	190,029
Total investment securities	893,265	850,615	802,495
Loans held for sale	12,625	18,818	6,874
Loans	3,962,342	3,831,285	3,748,010
Allowance for loan losses	(86,711)	(88,333)	(89,733)
Net loans	3,875,631	3,742,952	3,658,277
Premises and equipment (net of accumulated depreciation of $89,261 at June 30, 2012, $86,991 at December 31, 2011 and $84,731 at June 30, 2011)	67,382	65,997	65,252
Goodwill	113,414	113,414	113,414
Other intangible assets	10,607	11,472	12,327
Interest receivable and other assets	137,034	154,245	145,140
Total Assets	5,351,781	5,339,453	5,204,058
Deposits:
Noninterest-bearing	974,412	875,791	813,863
Interest-bearing	3,409,132	3,491,066	3,437,113
Total deposits	4,383,544	4,366,857	4,250,976
Interest payable and other liabilities	41,323	54,024	33,919
Short-term Borrowings	299,748	303,786	276,600
Federal Home Loan Bank (FHLB) advances	38,177	43,057	71,928
Total liabilities	4,762,792	4,767,724	4,633,423
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; issued and outstanding - 27,497,442 shares at June 30, 2012, 27,456,907 at December 31, 2011 and 27,456,907 at June 30, 2011	27,497	27,457	27,457
Additional paid-in capital	432,098	431,277	430,134
Retained earnings	153,558	138,324	126,477
Accumulated other comprehensive loss	(24,164)	(25,329)	(13,433)
Total shareholders' equity	588,989	571,729	570,635
Total Liabilities and Shareholders' Equity	$ 5,351,781	$ 5,339,453	$ 5,204,058