Loans - Schedule of composition of loan portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 6,501,404	$ 5,692,132
Interest Receivable	19,221	17,666
Loans and Leases Receivable, Recorded Investment	6,520,625	5,709,798
Commercial Financial And Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,185,110	1,072,786
Interest Receivable	4,393	4,603
Loans and Leases Receivable, Recorded Investment	1,189,503	1,077,389
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,609,413	1,283,045
Interest Receivable	5,571	4,750
Loans and Leases Receivable, Recorded Investment	1,614,984	1,287,795
Construction Real Estate Remaining Commercial [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	233,637	175,300
Interest Receivable	826	801
Loans and Leases Receivable, Recorded Investment	234,463	176,101
Construction Real Estate Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	96,574	70,541
Interest Receivable	228	151
Loans and Leases Receivable, Recorded Investment	96,802	70,692
Construction Real Estate Installment [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,488	2,433
Interest Receivable	4	7
Loans and Leases Receivable, Recorded Investment	1,492	2,440
Residential Real Estate Commercial [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	479,081	429,730
Interest Receivable	1,339	1,150
Loans and Leases Receivable, Recorded Investment	480,420	430,880
Residential Real Estate Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,176,316	1,134,278
Interest Receivable	1,381	1,227
Loans and Leases Receivable, Recorded Investment	1,177,697	1,135,505
Residential Real Estate Home Equity Line Of Credit [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	224,766	215,283
Interest Receivable	1,113	1,159
Loans and Leases Receivable, Recorded Investment	225,879	216,442
Residential Real Estate Installment [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	12,563	14,327
Interest Receivable	32	36
Loans and Leases Receivable, Recorded Investment	12,595	14,363
Consumer Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,452,375	1,292,136
Interest Receivable	4,314	3,756
Loans and Leases Receivable, Recorded Investment	1,456,689	1,295,892
Leases
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Net of Deferred Income	30,081	2,273
Interest Receivable	20	26
Loans and Leases Receivable, Recorded Investment	$ 30,101	$ 2,299

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
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