Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Cash and cash equivalents:
Cash and due from banks	$ 422,057	$ 229,901	$ 388,852
Interest-bearing deposits with banks	7,097	7,456	6,418
Federal funds sold and securities purchased under agreements to resell	164,228	180,512	194,253
Total cash and cash equivalents	593,382	417,869	589,523
Investment securities:
Securities held to maturity (fair value of $10,114, $10,233, and $11,058, respectively)	9,659	9,659	10,389
Securities available for sale, at fair value	841,661	806,766	795,741
Other investments	9,031	10,518	10,518
Total investment securities	860,351	826,943	816,648
Loans held for sale	73,055	61,934	56,407
Loans:
Loans, net	5,749,270	5,680,688	5,634,122
FDIC receivable for loss share agreements	11,035	22,161	43,766
Other real estate owned (covered of $8,172, $16,227, and $21,998, respectively; non-covered of $26,870, $26,499, and $31,735, respectively)	35,042	42,726	53,733
Premises and equipment, net	171,582	171,772	184,113
Bank owned life insurance	100,363	99,140	97,933
Deferred tax assets	45,911	42,692	66,780
Mortgage servicing rights	25,325	21,601	21,015
Core deposit and other intangibles	45,260	49,239	53,371
Goodwill	317,688	317,688	317,688
Other assets	56,720	71,774	58,587
Total assets	8,084,984	7,826,227	7,993,686
Deposits:
Noninterest-bearing	1,844,973	1,639,953	1,626,995
Interest-bearing	4,822,555	4,821,092	4,952,847
Total deposits	6,667,528	6,461,045	6,579,842
Federal funds purchased and securities sold under agreements to repurchase	287,903	221,541	280,595
Other borrowings	55,055	101,210	101,045
Other liabilities	50,719	57,511	79,186
Total liabilities	$ 7,061,205	$ 6,841,307	$ 7,040,668
Shareholders' equity:
Preferred stock-$.01 par value; authorized 10,000,000 shares; no shares issued and outstanding
Common stock - $2.50 par value; authorized 40,000,000 shares; 24,197,531, 24,150,702, and 24,130,006 shares issued and outstanding, respectively	$ 60,494	$ 60,377	$ 60,325
Surplus	704,625	701,764	699,324
Retained earnings	260,591	223,156	192,961
Accumulated other comprehensive income (loss)	(1,931)	(377)	408
Total shareholders' equity	1,023,779	984,920	953,018
Total liabilities and shareholders' equity	8,084,984	7,826,227	7,993,686
Non-acquired loans
Loans:
Loans, gross	3,788,399	3,467,826	3,174,625
Less allowance for non-acquired loan losses	(34,782)	(34,539)	(35,422)
Credit impaired | Acquired loans
Loans:
Loans, gross	823,981	919,402	1,047,336
Non-Credit impaired | Acquired loans
Loans:
Loans, gross	$ 1,171,672	$ 1,327,999	$ 1,447,583