Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Interest income:
Interest and fees on loans	$ 71,214	$ 55,383	$ 201,867	$ 158,781
Interest on debt securities:
Taxable	8,004	4,482	21,236	12,697
Nontaxable	969	263	2,277	816
Interest on interest-bearing deposits	572	306	1,722	777
Dividends on equity securities	319	323	794	729
Total interest income	81,078	60,757	227,896	173,800
Interest expense:
Interest-bearing transaction accounts	2,048	799	5,972	2,422
Money market accounts	6,959	5,423	20,470	13,221
Savings accounts	232	157	646	429
Certificates of deposit	3,970	2,878	11,060	7,115
Subordinated debentures and notes	1,956	1,483	5,562	4,305
Federal Home Loan Bank advances	2,203	1,729	5,297	4,435
Notes payable and other borrowings	664	195	1,785	561
Total interest expense	18,032	12,664	50,792	32,488
Net interest income	63,046	48,093	177,104	141,312
Provision for loan losses	1,833	2,263	5,031	4,524
Net interest income after provision for loan losses	61,213	45,830	172,073	136,788
Noninterest income:
Total noninterest income	13,564	8,410	34,758	27,645
Noninterest expense:
Employee compensation and benefits	20,845	16,297	60,884	49,370
Occupancy	3,179	2,394	9,004	7,142
Data processing	2,051	1,634	6,415	4,634
Professional fees	1,064	1,023	2,847	2,619
Merger related expenses	393	0	17,969	0
Other	10,707	8,574	30,012	24,519
Total noninterest expense	38,239	29,922	127,131	88,284
Income before income tax expense	36,538	24,318	79,700	76,149
Income tax expense	7,469	1,802	16,051	10,461
Net income	$ 29,069	$ 22,516	$ 63,649	$ 65,688
Earnings per common share
Basic (usd per share)	$ 1.09	$ 0.97	$ 2.46	$ 2.84
Diluted (usd per share)	$ 1.08	$ 0.97	$ 2.45	$ 2.81
Deposit Account [Member]
Noninterest income:
Total noninterest income	$ 3,246	$ 2,997	$ 9,547	$ 8,855
Fiduciary and Trust [Member]
Noninterest income:
Total noninterest income	2,661	2,012	7,314	6,267
Card Services Revenue [Member]
Noninterest income:
Total noninterest income	2,494	1,760	6,745	4,926
Tax credit activity, net [Member]
Noninterest income:
Total noninterest income	1,238	192	1,968	508
Gain on Sale of Securities, Excluding Acquisition Amount [Domain]
Noninterest income:
Total noninterest income	337	0	337	9
Financial Service, Other [Member]
Noninterest income:
Total noninterest income	$ 3,588	$ 1,449	$ 8,847	$ 7,080