Consolidated Statements of Financial Position (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Cash and cash equivalents:
Cash and cash due from banks	$ 137,586	$ 142,467	$ 122,010
Interest-bearing deposits with the Federal Reserve Bank	69,371	513,668	119,813
Total cash and cash equivalents	206,957	656,135	241,823
Investment securities:
Available-for-sale, at fair value	734,052	586,809	680,231
Held-to-maturity (fair value - $271,397 at June 30, 2013, $229,922 at December 31, 2012 and $213,852 at June 30, 2012)	274,715	229,977	213,034
Total investment securities	1,008,767	816,786	893,265
Loans held-for-sale	9,180	17,665	12,625
Loans	4,335,871	4,167,735	3,962,342
Allowance for loan losses	(82,184)	(84,491)	(86,711)
Net loans	4,253,687	4,083,244	3,875,631
Premises and equipment (net of accumulated depreciation of $96,036 at June 30, 2013, $93,207 at December 31, 2012 and $89,261 at June 30, 2012)	73,379	75,458	67,382
Goodwill	120,164	120,164	113,414
Other intangible assets	14,354	15,388	10,607
Interest receivable and other assets	119,723	132,412	137,034
Total Assets	5,806,211	5,917,252	5,351,781
Deposits:
Noninterest-bearing	1,107,453	1,085,857	974,412
Interest-bearing	3,706,732	3,835,586	3,409,132
Total deposits	4,814,185	4,921,443	4,383,544
Interest payable and other liabilities	35,460	54,716	41,323
Short-term borrowings	346,995	310,463	299,748
Federal Home Loan Bank (FHLB) advances	0	34,289	38,177
Total liabilities	5,196,640	5,320,911	4,762,792
Shareholders’ equity:
Preferred stock, no par value: Authorized - 200,000 shares, none issued	0	0	0
Common stock, $1 par value per share: Authorized - 45,000,000 shares; Issued and outstanding — 27,537,554 shares at June 30, 2013, 27,498,868 shares at December 31, 2012 and 27,497,442 shares at June 30, 2012	27,538	27,499	27,497
Additional paid-in capital	434,479	433,195	432,098
Retained earnings	182,619	166,766	153,558
Accumulated other comprehensive loss	(35,065)	(31,119)	(24,164)
Total shareholders’ equity	609,571	596,341	588,989
Total Liabilities and Shareholders’ Equity	$ 5,806,211	$ 5,917,252	$ 5,351,781