Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
INTEREST AND DIVIDEND INCOME
Loans, including fees	$ 393,166	$ 331,961	$ 272,007
Interest and dividends on securities:
Taxable	65,648	56,898	38,631
Tax-exempt	20,006	20,778	19,489
Total interest and dividends on securities	85,654	77,676	58,120
Other interest income	5,433	5,320	2,297
Total interest and dividend income	484,253	414,957	332,424
INTEREST EXPENSE
Interest bearing demand deposits	16,805	13,144	6,452
Money market deposits	8,024	5,016	2,775
Savings deposits	2,995	1,225	745
Certificates of deposit	15,631	12,450	10,108
Total interest expense on deposits	43,455	31,835	20,080
Federal Home Loan Bank borrowings	26,548	23,333	13,290
Other short-term borrowings	5,401	3,717	1,442
Subordinated debt and junior subordinated debt	8,945	8,836	7,317
Total interest expense	84,349	67,721	42,129
NET INTEREST INCOME	399,904	347,236	290,295
Provision for credit losses	11,198	7,764	9,986
Net interest income after provision for credit losses	388,706	339,472	280,309
NON-INTEREST INCOME
Electronic banking fees	22,634	23,300	19,183
Net securities brokerage revenue	6,990	7,186	6,672
Bank-owned life insurance	5,913	6,427	4,794
Mortgage banking income	8,219	5,840	5,053
Net securities gains (losses)	4,320	(900)	567
Net gain on other real estate owned and other assets	732	524	658
Other income	14,355	9,606	8,641
Total non-interest income	116,716	100,276	88,840
NON-INTEREST EXPENSE
Salaries and wages	132,485	114,602	97,361
Employee benefits	39,313	30,079	29,933
Net occupancy	22,505	19,165	17,101
Equipment	20,494	17,207	16,026
Marketing	6,062	5,368	5,720
FDIC insurance	1,956	3,242	3,504
Amortization of intangible assets	10,340	6,980	4,940
Restructuring and merger-related expense	16,397	17,860	945
Other operating expenses	62,656	50,721	45,330
Total non-interest expense	312,208	265,224	220,860
Income before provision for income taxes	193,214	174,524	148,289
Provision for income taxes	34,341	31,412	53,807
NET INCOME	$ 158,873	$ 143,112	$ 94,482
EARNINGS PER COMMON SHARE
Basic	$ 2.83	$ 2.93	$ 2.15
Diluted	$ 2.83	$ 2.92	$ 2.14
AVERAGE COMMON SHARES OUTSTANDING
Basic	56,108,084	48,889,041	44,003,208
Diluted	56,214,364	49,022,990	44,075,293
DIVIDENDS DECLARED PER COMMON SHARE	$ 1.24	$ 1.16	$ 1.04
Total Trust Fees [Member]
NON-INTEREST INCOME
NON-INTEREST INCOME	$ 26,579	$ 24,623	$ 22,740
Service Charges on Deposits [Member]
NON-INTEREST INCOME
NON-INTEREST INCOME	$ 26,974	$ 23,670	$ 20,532