Loans - Average Recorded Investment and Interest Income Recognized on Loans Individually Evaluated for Impairment (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Recorded investment	$ 48,144	$ 56,564	$ 70,426
Average recorded investment	51,041	67,070	79,496
Interest income recognized	1,890	2,708	4,777
Commercial, financial and agricultural
Financing Receivable, Impaired [Line Items]
Recorded investment	15,120	18,039	20,624
Average recorded investment	21,000	23,154	26,821
Interest income recognized	695	963	885
Commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded investment	28,426	18,142	24,474
Average recorded investment	23,024	21,692	22,828
Interest income recognized	1,047	903	884
Commercial
Financing Receivable, Impaired [Line Items]
Recorded investment	1,866	1,324	2,226
Average recorded investment	1,709	1,729	5,503
Interest income recognized	34	64	66
Commercial
Financing Receivable, Impaired [Line Items]
Recorded investment	2,732	19,059	23,102
Average recorded investment	5,308	20,490	24,341
Interest income recognized	$ 114	778	2,942
Consumer
Financing Receivable, Impaired [Line Items]
Average recorded investment		$ 5	$ 3

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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Amount of interest income recognized on a cash-basis method of accounting that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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