Consolidated Statements of Financial Position (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Cash and cash equivalents:
Cash and cash due from banks	$ 135,839	$ 142,467	$ 123,519
Interest-bearing deposits with the Federal Reserve Bank	357,271	513,668	315,201
Total cash and cash equivalents	493,110	656,135	438,720
Investment securities:
Available-for-sale, at fair value	705,146	586,809	646,578
Held-to-maturity (fair value - $275,866 at September 30, 2013, $229,922 at December 31, 2012 and $223,185 at September 30, 2012)	282,579	229,977	221,536
Total investment securities	987,725	816,786	868,114
Loans held-for-sale		17,665	15,075
Loans	4,522,671	4,167,735	4,019,159
Allowance for loan losses	(81,532)	(84,491)	(84,694)
Net loans	4,441,139	4,083,244	3,934,465
Premises and equipment (net of accumulated depreciation of $98,150 at September 30, 2013, $93,207 at December 31, 2012 and $91,203 at September 30, 2012)	73,690	75,458	67,796
Goodwill	120,164	120,164	113,414
Other intangible assets	13,865	15,388	10,243
Interest receivable and other assets	120,636	132,412	132,594
Total Assets	6,258,236	5,917,252	5,580,421
Deposits:
Noninterest-bearing	1,162,599	1,085,857	952,126
Interest-bearing	4,028,706	3,835,586	3,646,746
Total deposits	5,191,305	4,921,443	4,598,872
Interest payable and other liabilities	36,019	54,716	34,738
Short-term borrowings	357,595	310,463	311,471
Federal Home Loan Bank (FHLB) advances	0	34,289	37,237
Total liabilities	5,584,919	5,320,911	4,982,318
Shareholders’ equity:
Preferred stock, no par value: Authorized - 200,000 shares, none issued	0	0	0
Issued and outstanding — 29,778,250 shares at September 30, 2013, 27,498,868 shares at December 31, 2012 and 27,498,094 shares at September 30, 2012	29,778	27,499	27,498
Additional paid-in capital	487,176	433,195	432,627
Retained earnings	191,538	166,766	160,884
Accumulated other comprehensive loss	(35,175)	(31,119)	(22,906)
Total shareholders’ equity	673,317	596,341	598,103
Total Liabilities and Shareholders’ Equity	$ 6,258,236	$ 5,917,252	$ 5,580,421