CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
CASH FLOWS FROM OPERATING ACTIVITIES
Net income		$ 60,582	$ 57,408	$ 43,120
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation		5,333	5,225	4,451
Provision for loan/lease losses	$ 979	55,704	7,066	12,658
Deferred income taxes		(14,530)	6,364	6,292
Stock-based compensation expense		2,150	2,469	1,443
Deferred compensation expense accrued		3,821	2,773	1,824
Losses (gains) on other real estate owned, net		(317)	3,361	2,585
Amortization of premiums on securities, net		969	1,561	1,614
Caplet amortization		551
Securities (gains) losses, net		(2,484)	30
Loans originated for sale		(236,734)	(151,692)	(57,698)
Proceeds on sales of loans		241,553	152,633	58,353
Gains on sales of residential real estate loans		(4,680)	(2,571)	(901)
Gains on sales of government guaranteed portions of loans		(224)	(748)	(405)
Loss on liability extinguishment, net		3,907	436
Losses (gains) on sales of premises and equipment		(19)	753
Amortization of intangibles		2,149	2,266	1,692
Accretion of acquisition fair value adjustments, net		(3,271)	(4,344)	(5,527)
Increase in cash value of bank-owned life insurance		(1,904)	(1,973)	(1,632)
Loss (gain) on sale of subsidiary/certain assets and liabilities of subsidiary		158	(12,286)
Goodwill impairment		500	3,000
Decrease (increase) in other assets		12,802	(19,152)	(11,137)
Increase (decrease) in other liabilities		(13,839)	23,915	7,539
Net cash provided by operating activities		112,177	76,494	64,271
CASH FLOWS FROM INVESTING ACTIVITIES
Net decrease in federal funds sold		720	16,598	3,799
Net decrease (increase) in interest-bearing deposits at financial institutions		61,295	(69,984)	(14,508)
Proceeds from sales of other real estate owned		4,477	840	2,539
Activity in securities portfolio:
Purchases		(356,127)	(71,963)	(84,045)
Calls, maturities and redemptions		53,007	25,193	23,931
Paydowns		47,313	50,830	44,287
Sales		38,562	30,055	1,938
Activity in restricted investment securities:
Purchases		(4,600)	(5,859)	(5,409)
Redemptions		9,749	7,621	3,157
Proceeds from the liquidation of assets held for sale		10,999
Net increase in loans/leases originated and held for investment		(564,748)	(320,368)	(292,697)
Purchase of premises and equipment		(4,268)	(12,429)	(11,457)
Proceeds from sales of premises and equipment		101	2,562
Purchase of derivatives			(4,347)
Payment for termination of derivative		(808)
Net cash received (transferred) for sale of subsidiary/certain assets and liabilities of subsidiary		(154)	42,587
Net cash paid for acquisition				(5,183)
Net cash (used in) investing activities		(704,482)	(308,664)	(333,648)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase in deposit accounts		658,592	335,580	271,266
Net increase (decrease) in short-term borrowings		(7,993)	(14,193)	13,638
Activity in Federal Home Loan Bank advances:
Term advances		125,000	25,000	15,080
Calls and maturities		(121,600)	(35,000)	(40,000)
Net change in short-term and overnight advances		(94,300)	(52,465)	24,765
Prepayments		(55,274)	(30,323)
Activity in other borrowings:
Proceeds from other borrowings				9,000
Calls, maturities and scheduled principal payments			(11,937)	(12,550)
Prepayments			(46,313)
Paydown of revolving line of credit			(9,000)
Prepayments on brokered and public time deposits		29,153
Proceeds from subordinated notes		50,000	63,393
Payment of cash dividends on common stock		(3,779)	(3,767)	(3,300)
Proceeds from issuance of common stock, net		1,360	1,926	1,279
Repurchase and cancellation of shares		(3,779)
Net cash provided by financing activities		577,380	222,901	279,178
Net increase (decrease) in cash and due from banks		(14,925)	(9,269)	9,801
Cash and due from banks, beginning		76,254	85,523	75,722
Cash and due from banks, ending	76,254	61,329	76,254	85,523
Supplemental disclosure of cash flow information, cash payments for:
Interest		32,178	59,292	38,782
Income/franchise taxes		24,567	2,719	30
Supplemental schedule of noncash investing activities:
Change in accumulated other comprehensive income, unrealized gains on securities available for sale and derivative instruments, net		2,474	4,446	(3,206)
Exchange of shares of common stock in connection with payroll taxes for restricted stock and in connection with stock options exercised		(740)	(218)	(876)
Transfers of loans to other real estate owned		51	1,086	943
Increase in the fair value of back-to-back interest rate swap assets and liabilities		137,752	62,483	17,798
Dividends payable		947	947	939
Transfer of equity securities from securities available for sale to other assets at fair value				2,614
Assets Sold:
Total assets sold	11,966		11,966
Liabilities Sold:
Total liabilities sold	5,003		5,003
Gain (loss) on sale of subsidiary and certain assets and certain liabilities of subsidiary:		(158)	12,286
Fair value of assets acquired:
Cash and due from banks				4,651
Interest-bearing deposits at financial institutions				62,924
Securities				4,845
Loans receivable, net				477,337
Bank-owned life insurance				7,092
Premises and equipment, net				6,092
Restricted investment securities				3,654
Intangibles				10,064
Other assets				2,255
Total assets acquired				578,914
Fair value of liabilities assumed:
Deposits				439,579
Short-term borrowings				1,143
FHLB advances				74,540
Other borrowings				9,544
Other liabilities				8,878
Total liabilities assumed				533,684
Net assets acquired				45,230
Consideration paid:
Cash paid				9,834
Promissory note				1,500
Contingent commitment				2,000
Common stock				81,637
Total consideration paid				94,971
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Goodwill				49,741
RB&T
Activity in restricted investment securities:
Net cash received (transferred) for sale of subsidiary/certain assets and liabilities of subsidiary			42,600
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Bates Companies
Adjustments to reconcile net income to net cash provided by operating activities:
Loss (gain) on sale of subsidiary/certain assets and liabilities of subsidiary		158	(12,286)
Activity in restricted investment securities:
Net cash transferred in sale of subsidiary		(154)
Supplemental schedule of noncash investing activities:
Consideration received on sale of the Bates Companies		1,523
Supplemental disclosure of cash flow information for sale of subsidiary/certain assets and certain liabilities of subsidiary:
Cash proceeds		195	46,560
Assets Sold:
Cash and due from banks	3,973	349	3,973
Interest-bearing deposits at financial institutions	55,291		55,291
Securities held to maturity, at amortized cost	3,243		3,243
Securities available for sale, at fair value	21,874		21,874
Loans/leases receivable held for investment, net	357,931		357,931
Premises and equipment, net	5,612	19	5,612
Restricted investment securities	675		675
Other real estate owned, net	2,134		2,134
Other assets	3,228	2,259	3,228
Total assets sold	453,961	2,627	453,961
Liabilities Sold:
Noninterest-bearing deposits	69,802		69,802
Interest-bearing deposits	331,486		331,486
Short-term borrowings	1,158		1,158
Federal Home Loan Bank advances	15,000		15,000
Other liabilities	2,241	946	2,241
Total liabilities sold	419,687	946	419,687
Net assets sold	$ 34,274	1,681	34,274
Forgiveness of earn-out consideration		880
Note receivable consideration		448
Gain (loss) on sale of subsidiary and certain assets and certain liabilities of subsidiary:		(158)	12,286
Springfield Bancshares
Consideration paid:
Cash paid				3,700
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Goodwill				45,975
Bates Companies
Adjustments to reconcile net income to net cash provided by operating activities:
Goodwill impairment		$ 500	$ 3,000
Consideration paid:
Cash paid				1,400
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Goodwill				$ 3,766