Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Cash and cash equivalents:
Cash and due from banks	$ 227,264	$ 255,775	$ 212,042
Interest-bearing deposits with banks	362,773	117,635	348,602
Federal funds sold and securities purchased under agreements to resell	54,467	4,217	102,482
Total cash and cash equivalents	644,504	377,627	663,126
Investment securities:
Securities held to maturity (fair value of $1,284, $2,556 and $6,217, respectively)	1,274	2,529	6,095
Securities available for sale, at fair value	1,640,837	1,648,193	1,379,788
Other investments	23,479	23,047	14,726
Total investment securities	1,665,590	1,673,769	1,400,609
Loans held for sale	42,690	70,890	46,988
Loans:
Loans, net	10,589,521	10,575,417	7,868,840
Other real estate owned	11,073	11,203	20,007
Premises and equipment, net	253,605	255,565	203,505
Bank owned life insurance	226,222	225,132	149,562
Deferred tax assets	46,736	45,902	43,075
Mortgage servicing rights	34,196	31,119	30,063
Core deposit and other intangibles	70,376	73,789	55,461
Goodwill	999,592	999,586	595,711
Other assets	105,004	126,590	73,123
Total assets	14,689,109	14,466,589	11,150,070
Deposits:
Noninterest-bearing	3,120,818	3,047,432	2,599,111
Interest-bearing	8,542,280	8,485,334	6,434,327
Total deposits	11,663,098	11,532,766	9,033,438
Federal funds purchased and securities sold under agreements to repurchase	357,574	286,857	352,431
Other borrowings	215,589	216,385	107,988
Other liabilities	130,269	121,661	76,313
Total liabilities	12,366,530	12,157,669	9,570,170
Shareholders' equity:
Preferred stock - $.01 par value; authorized 10,000,000 shares; no shares issued and outstanding
Common stock - $2.50 par value; authorized 80,000,000, 80,000,000 and 40,000,000 shares, respectively; 36,783,438, 36,759,656 and 29,230,734 shares issued and outstanding, respectively	91,958	91,899	73,077
Surplus	1,807,989	1,807,601	1,132,173
Retained earnings	452,982	419,847	379,534
Accumulated other comprehensive loss	(30,350)	(10,427)	(4,884)
Total shareholders' equity	2,322,579	2,308,920	1,579,900
Total liabilities and shareholders' equity	14,689,109	14,466,589	11,150,070
Acquired credit impaired loans
Loans:
Loans, net	597,274	618,803	627,340
Total loans	601,358	623,430	631,896
Acquired non-credit impaired loans
Loans:
Loans, net	3,274,938	3,507,907	1,715,642
Total loans	3,274,938	3,507,907	1,715,642
Non-acquired loans
Loans:
Total loans	6,762,512	6,492,155	5,564,307
Less allowance for non-acquired loan losses	(45,203)	(43,448)	(38,449)
Loans, net	$ 6,717,309	$ 6,448,707	$ 5,525,858