Condensed Consolidated Statements of Net Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest income:
Loans, including fees	$ 280,825	$ 134,953	$ 581,566	$ 402,175
Investment securities:
Taxable	11,118	10,785	33,951	28,933
Tax-exempt	2,136	1,587	5,041	4,700
Federal funds sold, securities purchased under agreements to resell and interest-bearing deposits with banks	1,215	2,676	3,100	7,565
Total interest income	295,294	150,001	623,658	443,373
Interest expense:
Deposits	15,154	16,655	42,215	50,693
Federal funds purchased and securities sold under agreements to repurchase	509	612	1,515	2,037
Corporate and subordinated debentures	5,034	1,397	8,197	4,332
Other borrowings	4,249	3,964	10,813	8,492
Total interest expense	24,946	22,628	62,740	65,554
Net interest income	270,348	127,373	560,918	377,819
Provision for credit losses	29,797	4,028	217,804	9,220
Net interest income after provision for credit losses	240,551	123,345	343,114	368,599
Noninterest income:
Securities gains, net	15	437	15	2,687
Recoveries on acquired loans		1,401		4,615
Other	8,571	1,894	14,125	6,030
Total noninterest income	114,790	37,582	213,269	107,258
Noninterest expense:
Salaries and employee benefits	134,919	59,551	277,617	176,529
Occupancy expense	23,845	11,883	52,091	35,344
Information services expense	18,855	8,878	40,317	26,558
OREO expense and loan related	1,146	597	2,840	2,229
Pension plan termination expense				9,526
Amortization of intangibles	9,560	3,268	17,232	9,817
Supplies, printing and postage expense	2,755	1,418	5,870	4,417
Professional fees	4,385	2,442	9,727	7,463
FDIC assessment and other regulatory charges	2,849	228	7,310	3,218
Advertising and marketing	1,203	1,052	2,548	2,818
Merger and branch consolidation related expense	21,662		66,070	3,058
Other	15,708	7,047	37,624	23,033
Total noninterest expense	236,887	96,364	519,246	304,010
Earnings:
Income before provision for income taxes	118,454	64,563	37,137	171,847
Provision for income taxes	23,233	12,998	2,741	34,455
Net income	$ 95,221	$ 51,565	$ 34,396	$ 137,392
Earnings per common share:
Basic (in dollars per share)	$ 1.34	$ 1.51	$ 0.70	$ 3.94
Diluted (in dollars per share)	$ 1.34	$ 1.50	$ 0.69	$ 3.92
Weighted average common shares outstanding:
Basic (in shares)	70,905	34,057	49,330	34,859
Diluted (in shares)	71,076	34,300	49,636	35,069
Fees on deposit accounts
Noninterest income:
Noninterest income	$ 24,346	$ 19,725	$ 59,166	$ 56,274
Mortgage banking income
Noninterest income:
Noninterest income	48,022	6,115	81,040	13,807
Trust and investment services income
Noninterest income:
Noninterest income	7,404	7,320	21,931	22,309
Correspondent banking and capital market income
Noninterest income:
Noninterest income	$ 26,432	$ 690	$ 36,992	$ 1,536