Loans and Leases - Allowance for Credit Losses, Loans and Leases, Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 71,497	$ 68,216	$ 83,044	$ 35,331
Less: Allowance for credit losses, loans and leases	71,355	86,217	71,355	86,217	$ 83,044	$ 35,331
(Reversal of provision) provision for credit losses	101	21,577	(11,158)	42,029
Charge-offs	(1,141)	(3,947)	(1,626)	(4,618)
Recoveries	898	371	1,095	553
Ending balance	71,355	86,217	71,355	86,217
Loans and Leases Receivable, Allowance	71,355		71,355		83,044
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	12,922	0	12,922
Ending balance	0	12,922	0	12,922
Nonaccrual Troubled Debt Restructuring Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Pre-restructuring outstanding recorded investment	0	619	0	619
Accrual Troubled Debt Restructuring Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Pre-restructuring outstanding recorded investment	0	0	0	0
Commercial Financial And Agricultural [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	10,233	19,244	13,584	8,759
Less: Allowance for credit losses, loans and leases	11,734	16,736	11,734	16,736	13,584	8,759
(Reversal of provision) provision for credit losses	1,689	(2,034)	(1,389)	3,596
Charge-offs	(350)	(744)	(688)	(1,225)
Recoveries	162	270	227	322
Ending balance	11,734	16,736	11,734	16,736
Commercial Financial And Agricultural [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	5,284	0	5,284
Ending balance	0	5,284	0	5,284
Commercial Financial And Agricultural [Member] | Nonaccrual Troubled Debt Restructuring Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Pre-restructuring outstanding recorded investment	0	619	0	619
Real-Estate Commercial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	45,459	34,810	52,230	15,750
Less: Allowance for credit losses, loans and leases	43,194	50,671	43,194	50,671	52,230	15,750
(Reversal of provision) provision for credit losses	(2,347)	18,663	(9,118)	31,480
Charge-offs	(523)	(2,802)	(523)	(2,802)
Recoveries	605	0	605	35
Ending balance	43,194	50,671	43,194	50,671
Real-Estate Commercial [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	6,208	0	6,208
Ending balance	0	6,208	0	6,208
Real-Estate Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,799	3,117	3,298
Less: Allowance for credit losses, loans and leases	3,649	4,130	3,649	4,130	3,298
(Reversal of provision) provision for credit losses	850	1,013	351	1,655
Charge-offs	0		0	0
Recoveries	0		0	0
Ending balance	3,649	4,130	3,649	4,130
Loans and Leases Receivable, Allowance		4,130		4,130		2,446
Real-Estate Construction [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	29	0	29
Ending balance	0	29	0	29
Real Estate Residential Secured For Business Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	6,692	5,906	7,317	2,622
Less: Allowance for credit losses, loans and leases	6,747	8,180	6,747	8,180	7,317	2,622
(Reversal of provision) provision for credit losses	260	2,365	(419)	3,147
Charge-offs	(227)	(96)	(227)	(99)
Recoveries	22	5	76	8
Ending balance	6,747	8,180	6,747	8,180
Real Estate Residential Secured For Business Purpose [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	2,502	0	2,502
Ending balance	0	2,502	0	2,502
Real Estate Residential Secured For Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,056	2,121	3,055
Less: Allowance for credit losses, loans and leases	2,620	2,669	2,620	2,669	3,055
(Reversal of provision) provision for credit losses	(436)	548	(435)	662
Charge-offs	0	0	0	0
Recoveries	0	0	0
Ending balance	2,620	2,669	2,620	2,669
Loans and Leases Receivable, Allowance		2,669		2,669		2,713
Real Estate Residential Secured For Personal Purpose [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	(706)	0	(706)
Ending balance	0	(706)	0	(706)
Real Estate Home Equity Secured For Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,257	795	1,176
Less: Allowance for credit losses, loans and leases	1,124	1,071	1,124	1,071	1,176
(Reversal of provision) provision for credit losses	(155)	273	(76)
Charge-offs	0		0	0
Recoveries	22	3	24
Ending balance	1,124	1,071	1,124	1,071
Real Estate Home Equity Secured For Personal Purpose [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	(364)	0	(364)
Ending balance	0	(364)	0	(364)
Loans to Individuals [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	447	600	533	470
Less: Allowance for credit losses, loans and leases	319	771	319	771	533	470
(Reversal of provision) provision for credit losses	(145)	239	(203)	286
Charge-offs	(23)	(93)	(79)	(128)
Recoveries	40	25	68	39
Ending balance	319	771	319	771
Loans to Individuals [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	104	0	104
Ending balance	0	104	0	104
Lease Financings [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,404	1,473	1,701	1,311
Less: Allowance for credit losses, loans and leases	1,815	1,839	1,815	1,839	1,701	1,311
(Reversal of provision) provision for credit losses	382	510	128	886
Charge-offs	(18)	(212)	(109)	(364)
Recoveries	47	68	95	141
Ending balance	1,815	1,839	1,815	1,839
Lease Financings [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	(135)	0	(135)
Ending balance	0	(135)	0	(135)
Unallocated [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	150	150	150	184
Less: Allowance for credit losses, loans and leases	150	150	150	150	150	184
(Reversal of provision) provision for credit losses	0	0	0	(34)
Ending balance	150	150	150	150
Unallocated [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0	0	0	0
Ending balance	0	0	0	0
Residential And Home Equity Secured For Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				1,076
Less: Allowance for credit losses, loans and leases		1,071		1,071		$ 1,076
(Reversal of provision) provision for credit losses				351
Charge-offs				0
Recoveries				8
Ending balance		1,071		1,071
Paycheck Protection Program Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	0		0
Less: Allowance for credit losses, loans and leases	3	0	3	0	$ 0
(Reversal of provision) provision for credit losses	3		3
Charge-offs	0		0
Recoveries	0		0
Ending balance	3	$ 0	3	$ 0
Paycheck Protection Program Loans | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Less: Allowance for credit losses, loans and leases	0		0
Ending balance	$ 0		$ 0