Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Cash and cash equivalents:
Cash and due from banks	$ 168,774	$ 178,664	$ 156,489
Interest-bearing deposits with banks	66,335	218,883	492,346
Federal funds sold and securities purchased under agreements to resell	272,408	298,247	240,545
Total cash and cash equivalents	507,517	695,794	889,380
Investment securities:
Securities held to maturity (fair value of $7,076, $9,723 and $9,758, respectively)	6,851	9,314	9,314
Securities available for sale, at fair value	925,374	1,009,541	885,798
Other investments	9,482	8,893	9,031
Total investment securities	941,707	1,027,748	904,143
Loans held for sale	57,052	41,649	48,985
Loans:
Loans, net	6,489,068	5,970,044	5,835,646
FDIC indemnification asset		4,401	7,942
Other real estate owned (covered of $0, $5,751 and $5,465, respectively; non-covered of $22,211, $24,803 and $25,913, respectively)	22,211	30,554	31,378
Premises and equipment, net	179,450	174,537	174,662
Bank owned life insurance	103,427	101,588	100,967
Deferred tax assets	25,357	37,827	40,090
Mortgage servicing rights	23,064	26,202	24,665
Core deposit and other intangibles	41,738	47,425	49,982
Goodwill	338,340	338,340	338,342
Other assets	68,234	61,239	53,694
Total assets	8,797,165	8,557,348	8,499,876
Deposits:
Noninterest-bearing	2,176,155	1,976,480	1,927,309
Interest-bearing	5,071,251	5,123,948	5,150,700
Total deposits	7,247,406	7,100,428	7,078,009
Federal funds purchased and securities sold under agreements to repurchase	305,268	288,231	260,521
Other borrowings	55,306	55,158	55,107
Other liabilities	65,053	54,147	57,927
Total liabilities	7,673,033	7,497,964	7,451,564
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; 24,209,122, 24,162,657 and 24,211,793 shares issued and outstanding, respectively	60,523	60,407	60,529
Surplus	705,124	703,929	706,227
Retained earnings	354,490	298,919	279,681
Accumulated other comprehensive loss	3,995	(3,871)	1,875
Total shareholders' equity	1,124,132	1,059,384	1,048,312
Total liabilities and shareholders' equity	8,797,165	8,557,348	8,499,876
Acquired credit impaired loans
Loans:
Loans, net	632,617	733,870	768,606
Total loans	636,020		773,080
Less allowance for loan losses		(3,706)
Loans, net	632,617	635,411	665,277
Non-acquired loans
Loans:
Total loans	5,008,113	4,220,726	3,994,716
Less allowance for loan losses	(37,319)	(34,090)	(35,116)
Loans, net	4,970,794	4,186,636	3,959,600
Acquired non-credit impaired loans
Loans:
Loans, net	885,657	1,049,538	1,107,440
Total loans	885,657		1,107,440
Loans, net	$ 885,657	$ 1,041,491	$ 1,099,450