Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest income:
Loans, including fees	$ 129,852	$ 93,600	$ 256,893	$ 185,352
Investment securities:
Taxable	9,048	7,020	17,836	14,251
Tax-exempt	1,614	1,397	3,173	2,827
Federal funds sold and securities purchased under agreements to resell	1,218	762	1,878	1,335
Total interest income	141,732	102,779	279,780	203,765
Interest expense:
Deposits	10,009	2,661	16,922	5,158
Federal funds purchased and securities sold under agreements to repurchase	642	240	1,096	480
Other borrowings	1,519	847	3,227	1,734
Total interest expense	12,170	3,748	21,245	7,372
Net interest income	129,562	99,031	258,535	196,393
Provision for loan losses	4,478	2,313	6,932	6,020
Net interest income after provision for loan losses	125,084	96,718	251,603	190,373
Noninterest income:
Fees on deposit accounts	22,612	19,897	45,155	39,398
Mortgage banking income	3,317	5,195	8,265	10,764
Trust and investment services income	7,567	6,452	15,081	12,393
Securities gains (losses), net	(641)	110	(641)	110
Recoveries on acquired loans	2,167	2,171	5,142	3,703
Other	2,503	1,491	5,078	3,165
Total noninterest income	37,525	35,316	78,080	69,533
Noninterest expense:
Salaries and employee benefits	55,026	47,580	117,491	96,466
Net occupancy expense	7,815	6,048	15,981	12,436
Information services expense	8,903	6,413	18,641	12,773
Furniture and equipment expense	4,519	3,877	9,145	7,671
OREO expense and loan related	1,037	1,753	2,698	3,895
Bankcard expense	311	628	1,002	1,180
Amortization of intangibles	3,722	2,495	7,135	5,002
Supplies, printing and postage expense	1,406	1,570	2,798	3,224
Professional fees	1,898	1,599	3,597	3,372
FDIC assessment and other regulatory charges	3,277	989	4,540	2,111
Advertising and marketing	1,163	989	1,899	1,548
Merger and branch consolidation related expenses	14,096	4,307	25,392	25,331
Other	7,333	6,033	13,650	11,777
Total noninterest expense	110,506	84,281	223,969	186,786
Earnings:
Income before provision for income taxes	52,103	47,753	105,714	73,120
Provision for income taxes	11,644	15,930	22,929	23,033
Net income	$ 40,459	$ 31,823	$ 82,785	$ 50,087
Earnings per common share:
Basic (in dollars per share)	$ 1.10	$ 1.09	$ 2.25	$ 1.73
Diluted (in dollars per share)	1.09	1.08	2.24	1.71
Dividends per common share (in dollars per share)	$ 0.34	$ 0.33	$ 0.67	$ 0.66
Weighted-average common shares outstanding:
Basic (in shares)	36,677	29,095	36,657	28,985
Diluted (in shares)	36,929	29,365	36,910	29,252