Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Cash and cash equivalents:
Cash and due from banks	$ 269,480	$ 184,611	$ 292,625
Interest-bearing deposits with banks	7,382	32,632	4,720
Federal funds sold and securities purchased under agreements to resell	226,166	262,218	347,821
Total cash and cash equivalents	503,028	479,461	645,166
Investment securities:
Securities held to maturity (fair value of $11,019, $12,891, and $12,992, respectively)	10,389	12,426	12,426
Securities available for sale, at fair value	805,114	786,791	626,798
Other investments	10,518	13,386	13,386
Total investment securities	826,021	812,603	652,610
Loans held for sale	56,595	30,586	51,207
Loans:
Loans, net	5,627,739	5,652,458	5,687,059
FDIC receivable for loss share agreements	30,983	86,447	108,149
Other real estate owned (covered of $18,961, $27,520, and $40,543, respectively; non-covered of $32,289, $37,398, and $35,330, respectively)	51,250	64,918	75,873
Premises and equipment, net	173,425	188,114	184,959
Bank owned life insurance	98,505	97,197	96,058
Deferred tax assets	60,322	72,914	73,135
Mortgage servicing rights	22,052	20,729	18,908
Core deposit and other intangibles	51,291	59,908	62,195
Goodwill	317,688	317,688	317,688
Other assets	61,189	48,475	55,434
Total assets	7,880,088	7,931,498	8,028,441
Deposits:
Noninterest-bearing	1,654,308	1,487,798	1,477,793
Interest-bearing	4,863,920	5,067,699	5,181,315
Total deposits	6,518,228	6,555,497	6,659,108
Federal funds purchased and securities sold under agreements to repurchase	231,229	211,401	233,792
Other borrowings	101,127	102,060	101,347
Other liabilities	62,509	81,071	64,168
Total liabilities	6,913,093	6,950,029	7,058,415
Shareholders' equity :
Preferred stock - $.01 par value; authorized 10,000,000 shares; 0, 65,000, and 65,000 shares issued and outstanding, respectively		1	1
Common stock - $2.50 par value; authorized 40,000,000 shares; 24,135,220, 24,104,124, and 24,066,545 shares issued and outstanding, respectively	60,338	60,260	60,166
Surplus	700,579	762,354	760,507
Retained earnings	207,219	168,577	159,980
Accumulated other comprehensive loss	(1,141)	(9,723)	(10,628)
Total shareholders' equity	966,995	981,469	970,026
Total liabilities and shareholders' equity	7,880,088	7,931,498	8,028,441
Non-acquired loans
Loans:
Loans, allowance	(34,804)	(34,331)	(36,145)
Loans, gross	3,304,708	2,865,216	2,741,242
Credit impaired | Acquired loans
Loans:
Loans, net	980,492	1,220,638	1,316,628
Non-credit impaired | Acquired loans
Loans:
Loans, gross	$ 1,377,343	$ 1,600,935	$ 1,665,334