Loans and Leases - Allowance for Credit Losses, Loan and Leases, Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 86,217	$ 32,600	$ 35,331	$ 29,364
Allowance for credit losses, loans and lease	91,870	33,662	91,870	29,364	$ 35,331
Provision for credit losses	5,618	1,530	47,647	6,291
Charge-offs	(448)	(844)	(5,066)	(2,769)
Recoveries	483	376	1,036	776
Ending balance	91,870	33,662	91,870	33,662
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					12,922
Commercial Financial And Agricultural [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	16,736	9,129	8,759	7,983
Allowance for credit losses, loans and lease	14,547	9,250	14,547	9,250	8,759
Provision for credit losses	(2,401)	222	1,195	2,753
Charge-offs	(142)	(283)	(1,367)	(1,769)
Recoveries	354	182	676	283
Ending balance	14,547	9,250	14,547	9,250
Commercial Financial And Agricultural [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					5,284
Real-Estate Commercial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	50,671		15,750
Allowance for credit losses, loans and lease	58,152		15,750		15,750
Provision for credit losses	7,481		38,961
Charge-offs	0		(2,802)
Recoveries	0		35
Ending balance	58,152		58,152
Real-Estate Commercial [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					6,208
Real-Estate Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,130		2,446
Allowance for credit losses, loans and lease	4,485		4,485		2,446
Provision for credit losses	355		2,010
Charge-offs	0		0
Recoveries	0		0
Ending balance	4,485		4,485
Real-Estate Construction [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					29
Real Estate Commercial And Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		15,478		13,903
Allowance for credit losses, loans and lease		15,821		13,903
Provision for credit losses		593		2,151
Charge-offs		(251)		(325)
Recoveries		1		92
Ending balance		15,821		15,821
Real Estate Residential Secured For Business Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	8,180	2,478	2,622	2,236
Allowance for credit losses, loans and lease	8,366	2,685	2,622	2,685	2,622
Provision for credit losses	251	109	3,398	341
Charge-offs	(88)	0	(187)	0
Recoveries	23	98	31	108
Ending balance	8,366	2,685	8,366	2,685
Real Estate Residential Secured For Business Purpose [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					2,502
Real Estate Residential Secured For Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,669		2,713
Allowance for credit losses, loans and lease	2,716		2,716		2,713
Provision for credit losses	47		709
Charge-offs	0		0
Recoveries	0		0
Ending balance	2,716		2,716
Real Estate Residential Secured For Personal Purpose [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					(706)
Real Estate Home Equity Secured For Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,071		1,076
Allowance for credit losses, loans and lease	1,279		1,279		1,076
Provision for credit losses	204		555
Charge-offs	0		0
Recoveries	4		12
Ending balance	1,279		1,279
Real Estate Home Equity Secured For Personal Purpose [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					(364)
Residential And Home Equity Secured For Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		3,518		3,199
Allowance for credit losses, loans and lease		3,612		3,199
Provision for credit losses		273		595
Charge-offs		(183)		(198)
Recoveries		4		16
Ending balance		3,612		3,612
Loans to Individuals [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	771	481	470	484
Allowance for credit losses, loans and lease	549	475	549	484	470
Provision for credit losses	(170)	47	116	142
Charge-offs	(69)	(73)	(197)	(209)
Recoveries	17	20	56	58
Ending balance	549	475	549	475
Loans to Individuals [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					104
Lease Financings [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,839	1,241	1,311	1,288
Allowance for credit losses, loans and lease	1,626	1,234	1,626	1,234	1,311
Provision for credit losses	(149)	(24)	737	(5)
Charge-offs	(149)	(54)	(513)	(268)
Recoveries	85	71	226	219
Ending balance	1,626	1,234	1,626	1,234
Lease Financings [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					(135)
Unallocated [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	150	275	184	271
Allowance for credit losses, loans and lease	150	585	184	585	184
Provision for credit losses	0	310	(34)	314
Ending balance	$ 150	$ 585	$ 150	$ 585
Unallocated [Member] | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, loans and lease					$ 0