Consolidated Statements of Financial Position (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Cash and cash equivalents:
Cash and cash due from banks	$ 101,501	$ 142,467	$ 120,435
Interest-bearing deposits with the Federal Reserve Bank	477,225	513,668	353,243
Total cash and cash equivalents	578,726	656,135	473,678
Investment securities:
Available-for-sale, at fair value	703,622	586,809	676,007
Held-to-maturity (fair value - $261,405 at March 31, 2013, $229,922 at December 31, 2012 and $192,372 at March 31, 2012)	257,749	229,977	191,297
Total investment securities	961,371	816,786	867,304
Loans held-for-sale	14,850	17,665	25,080
Loans	4,185,261	4,167,735	3,843,098
Allowance for loan losses	(82,834)	(84,491)	(87,785)
Net loans	4,102,427	4,083,244	3,755,313
Premises and equipment (net of accumulated depreciation of $94,068 at March 31, 2013, $93,207 at December 31, 2012 and $88,603 at March 31, 2012)	73,501	75,458	66,661
Goodwill	120,164	120,164	113,414
Other intangible assets	14,902	15,388	10,939
Interest receivable and other assets	124,587	132,412	139,130
Total Assets	5,990,528	5,917,252	5,451,519
Deposits:
Noninterest-bearing	1,086,986	1,085,857	914,523
Interest-bearing	3,920,372	3,835,586	3,546,861
Total deposits	5,007,358	4,921,443	4,461,384
Interest payable and other liabilities	30,931	54,716	32,809
Short-term borrowings	347,484	310,463	335,082
Federal Home Loan Bank (FHLB) advances	0	34,289	42,120
Total liabilities	5,385,773	5,320,911	4,871,395
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 — March 31, 2013 - 27,532,377 shares, December 31, 2012 - 27,498,868 shares and March 31, 2012 - 27,491,026 shares	27,532	27,499	27,491
Additional paid-in capital	433,648	433,195	431,549
Retained earnings	174,209	166,766	145,195
Accumulated other comprehensive loss	(30,634)	(31,119)	(24,111)
Total shareholders’ equity	604,755	596,341	580,124
Total Liabilities and Shareholders’ Equity	$ 5,990,528	$ 5,917,252	$ 5,451,519