Allowance for Loan Losses - Allowance Calculation at the Segment Level and Adjusted Beginning Balance for the Allowance for Credit Losses (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Reserve Estimate Methodology, Historical Loss Period Factor	72 months
Beginning balance	$ 59,468	$ 55,537	$ 68,444
Charge-offs	24,780	19,153	61,268
Recoveries	(26,997)	(19,669)	(12,942)
Net charge-offs (recoveries)	(2,217)	(516)	48,326
Provision (Recovery)	(7,333)	3,415	35,419
Ending balance	54,352	59,468	55,537
Commercial, financial and agricultural
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	14,218	15,635	16,950
Charge-offs	3,779	6,160	26,847
Recoveries	(1,003)	(1,314)	(1,066)
Net charge-offs (recoveries)	2,776	4,846	25,781
Provision (Recovery)	(723)	3,429	24,466
Ending balance	10,719	14,218	15,635
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	15,899	11,736	15,539
Charge-offs	8,003	1,832	10,454
Recoveries	(7,759)	(726)	(783)
Net charge-offs (recoveries)	244	1,106	9,671
Provision (Recovery)	(6,847)	5,269	5,868
Ending balance	8,808	15,899	11,736
Construction real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	6,855	6,841	14,433
Charge-offs	1,316	1,791	9,985
Recoveries	(12,572)	(9,378)	(2,979)
Net charge-offs (recoveries)	(11,256)	(7,587)	7,006
Provision (Recovery)	(9,459)	(7,573)	(586)
Ending balance	8,652	6,855	6,841
Residential real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	14,251	14,759	15,692
Charge-offs	3,944	3,207	8,607
Recoveries	(2,985)	(6,000)	(5,559)
Net charge-offs (recoveries)	959	(2,793)	3,048
Provision (Recovery)	1,480	(3,301)	2,115
Ending balance	14,772	14,251	14,759
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	8,245	6,566	5,830
Charge-offs	7,738	6,163	5,375
Recoveries	(2,671)	(2,249)	(2,555)
Net charge-offs (recoveries)	5,067	3,914	2,820
Provision (Recovery)	8,223	5,593	3,556
Ending balance	11,401	8,245	6,566
Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	0	0	0
Charge-offs	0	0	0
Recoveries	(7)	(2)	0
Net charge-offs (recoveries)	(7)	(2)	0
Provision (Recovery)	(7)	(2)	0
Ending balance	$ 0	$ 0	$ 0

Allowance for Loan and Lease Losses, Reserve Estimate Methodology, Historical Loss Period Factor

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- Definition

Financing Receivables Allowance For Credit Losses Net Charge Offs

+ References

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- Definition

Amount of recovery of financing receivables doubtful of collection that were previously charged off.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(4)

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- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(d))

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-Number 210

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

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- Definition

Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

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