Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Cash and cash equivalents:
Cash and due from banks	$ 183,170	$ 178,664	$ 149,620
Interest-bearing deposits with banks	250,229	218,883	315,206
Federal funds sold and securities purchased under agreements to resell	263,878	298,247	165,908
Total cash and cash equivalents	697,277	695,794	630,734
Investment securities:
Securities held to maturity (fair value of $8,280, $9,723 and $10,232, respectively)	7,920	9,314	9,659
Securities available for sale, at fair value	978,047	1,009,541	808,396
Other investments	9,539	8,893	9,031
Total investment securities	995,506	1,027,748	827,086
Loans held for sale	34,933	41,649	87,342
Loans:
Loans, net	6,129,228	5,970,044	5,666,720
Loans, gross	4,472,668	4,220,726	3,586,405
Less allowance for non-acquired loan losses	(35,115)	(34,090)	(33,538)
FDIC indemnification asset	2,091	4,401	16,713
Other real estate owned (covered of $4,222, $5,751 and $12,026, respectively; non-covered of $21,731, $24,803 and $24,070, respectively)	25,953	30,554	36,096
Premises and equipment, net	176,412	174,537	171,565
Bank owned life insurance	102,199	101,588	99,751
Deferred tax assets	32,045	37,827	40,629
Mortgage servicing rights	23,697	26,202	21,510
Core deposit and other intangibles	45,521	47,425	47,223
Goodwill	338,340	338,340	317,688
Other assets	67,555	61,239	58,525
Total assets	8,670,757	8,557,348	8,021,582
Deposits:
Noninterest-bearing	2,020,632	1,976,480	1,757,302
Interest-bearing	5,141,316	5,123,948	4,876,355
Total deposits	7,161,948	7,100,428	6,633,657
Federal funds purchased and securities sold under agreements to repurchase	312,034	288,231	276,774
Other borrowings	55,210	55,158	55,003
Other liabilities	59,511	54,147	48,584
Total liabilities	$ 7,588,703	$ 7,497,964	$ 7,014,018
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; 24,177,833, 24,162,657 and 24,156,759 shares issued and outstanding, respectively	$ 60,445	$ 60,407	$ 60,392
Surplus	701,462	703,929	702,648
Retained earnings	316,642	298,919	241,526
Accumulated other comprehensive loss	3,505	(3,871)	2,998
Total shareholders' equity	1,082,054	1,059,384	1,007,564
Total liabilities and shareholders' equity	8,670,757	8,557,348	8,021,582
Acquired credit impaired loans
Loans:
Loans, net	692,437	733,870	866,504
Acquired non-cedit impaired loans
Loans:
Loans, net	$ 999,238	$ 1,049,538	$ 1,247,349