Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Interest and fees on loans	$ 269,406	$ 217,212	$ 185,452
Interest on debt securities:
Taxable	29,030	17,469	14,551
Nontaxable	3,515	1,074	1,283
Interest on interest-earning deposits	2,128	1,141	804
Dividends on equity securities	1,055	906	449
Total interest income	305,134	237,802	202,539
Interest expense:
Interest-bearing transaction accounts	7,592	3,643	2,195
Money market accounts	26,267	19,361	8,708
Savings accounts	841	597	459
Certificates of Deposit	15,156	10,168	5,838
Subordinated debentures and notes	7,507	5,798	5,095
FHLB advances	6,668	5,556	2,356
Notes payable and other borrowings	2,386	774	584
Total interest expense	66,417	45,897	25,235
Net interest income	238,717	191,905	177,304
Provision for loan losses	6,372	6,644	10,130
Net interest income after provision for loan losses	232,345	185,261	167,174
Noninterest income:
Total noninterest income	49,176	38,347	34,394
Noninterest expense:
Employee compensation and benefits	81,295	66,039	61,388
Occupancy	12,465	9,550	9,057
Data processing	8,242	6,321	6,272
Professional fees	3,683	3,134	3,813
Merger Related Expenses	17,969	1,271	6,462
Other	41,831	32,716	28,059
Total noninterest expense	165,485	119,031	115,051
Income before income tax expense	116,036	104,577	86,517
Income tax expense	23,297	15,360	38,327
Net income	$ 92,739	$ 89,217	$ 48,190
Earnings per common share
Basic (usd per share)	$ 3.56	$ 3.86	$ 2.10
Diluted (usd per share)	$ 3.55	$ 3.83	$ 2.07
Deposit Account [Member]
Noninterest income:
Total noninterest income	$ 12,801	$ 11,749	$ 11,043
Fiduciary and Trust [Member]
Noninterest income:
Total noninterest income	9,932	8,241	8,102
Card Services Revenue [Member]
Noninterest income:
Total noninterest income	9,154	6,686	5,433
Tax credit activity, net [Member]
Noninterest income:
Total noninterest income	5,393	2,820	2,581
Gain on Sale of Securities, Excluding Acquisition Amount [Domain]
Noninterest income:
Total noninterest income	243	9	22
Financial Service, Other [Member]
Noninterest income:
Total noninterest income	$ 11,653	$ 8,842	$ 7,213