Allowance for Credit Losses - Recorded Investments in Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	$ 44,350	$ 51,179
Collectively evaluated for impairment	10,889,297	9,466,195
Loans, net of unearned income	10,933,647	9,689,638
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, net of unearned income		172,264
Commercial, financial, agriculture
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	16,091	8,460
Collectively evaluated for impairment	2,520,893	1,329,974
Loans, net of unearned income	2,536,984	1,367,972
Commercial, financial, agriculture \| Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, net of unearned income		29,538
Real estate - construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	497	12,416
Collectively evaluated for impairment	857,607	813,204
Loans, net of unearned income	858,104	826,483
Real estate - construction \| Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, net of unearned income		863
Real estate - 1-4 family mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	5,379	20,262
Collectively evaluated for impairment	2,692,929	2,810,808
Loans, net of unearned income	2,698,308	2,866,613
Real estate - 1-4 family mortgage \| Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, net of unearned income		35,543
Real estate - commercial mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	21,764	9,550
Collectively evaluated for impairment	4,533,088	4,131,582
Loans, net of unearned income	4,554,852	4,244,265
Real estate - commercial mortgage \| Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, net of unearned income		103,133
Installment and Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	619	491
Collectively evaluated for impairment	208,918	380,627
Loans, net of unearned income	$ 209,537	384,305
Installment and Other \| Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, net of unearned income		$ 3,187

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount, before allowance for credit loss, of financing receivable.

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