Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest income:
Loans, including fees	$ 132,043	$ 95,864	$ 388,936	$ 281,216
Investment securities:
Taxable	8,890	6,646	26,726	20,897
Tax-exempt	1,521	1,320	4,695	4,147
Federal funds sold and securities purchased under agreements to resell	1,106	581	2,983	1,916
Total interest income	143,560	104,411	423,340	308,176
Interest expense:
Deposits	13,220	2,974	30,142	8,132
Federal funds purchased and securities sold under agreements to repurchase	599	276	1,696	756
Other borrowings	1,452	842	4,678	2,576
Total interest expense	15,271	4,092	36,516	11,464
Net interest income	128,289	100,319	386,824	296,712
Provision for loan losses	3,117	2,062	10,049	8,082
Net interest income after provision for loan losses	125,172	98,257	376,775	288,630
Noninterest income:
Securities gains (losses), net	(11)	1,278	(652)	1,388
Other-than-temporary impairment losses		(753)		(753)
Recoveries on acquired loans	1,238	1,944	6,379	5,647
Other	2,659	1,367	7,738	4,532
Total noninterest income	32,027	33,736	110,107	103,268
Noninterest expense:
Salaries and employee benefits	57,934	47,245	175,425	143,711
Net occupancy expense	7,630	6,214	23,611	18,650
Information services expense	7,804	6,003	26,445	18,776
Furniture and equipment expense	4,605	3,751	13,750	11,422
OREO expense and loan related	(19)	1,753	2,679	5,648
Bankcard expense	379	444	1,381	1,623
Amortization of intangibles	3,537	2,494	10,672	7,496
Supplies, printing and postage expense	1,561	1,491	4,359	4,715
Professional fees	2,138	1,265	5,735	4,637
FDIC assessment and other regulatory charges	2,525	918	7,065	3,029
Advertising and marketing	1,049	852	2,948	2,400
Merger and branch consolidation related expense	4,476	1,551	29,868	26,882
Other	6,675	5,289	20,325	17,066
Total noninterest expense	100,294	79,270	324,263	266,055
Earnings:
Income before provision for income taxes	56,905	52,723	162,619	125,843
Provision for income taxes	9,823	17,677	32,752	40,710
Net income	$ 47,082	$ 35,046	$ 129,867	$ 85,133
Earnings per common share:
Basic (in dollars per share)	$ 1.28	$ 1.20	$ 3.53	$ 2.92
Diluted (in dollars per share)	1.28	1.19	3.52	2.90
Dividends per common share (in dollars per share)	$ 0.35	$ 0.33	$ 1.02	$ 0.99
Weighted-average common shares outstanding:
Basic (in shares)	36,645	29,115	36,657	29,023
Diluted (in shares)	36,893	29,385	36,909	29,291
Fees on deposit accounts
Noninterest income:
Noninterest income	$ 17,790	$ 20,144	$ 62,945	$ 59,541
Mortgage banking income
Noninterest income:
Noninterest income	2,824	3,446	11,089	14,210
Trust and investment services income
Noninterest income:
Noninterest income	$ 7,527	$ 6,310	$ 22,608	$ 18,703