Represents the number of outstanding short-term FHLB advances.

No definition available.

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- Definition

The cost of acquiring the advances.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average remaining maturity on FHLB advances

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Interest expense incurred during the reporting period on short-term borrowings associated with Federal Home Loan Bank and Federal Reserve Bank advances.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of addition (reduction) to the amount at which a liability could be incurred (settled) in a current transaction between willing parties.

+ References

No definition available.

+ Details

Name:	us-gaap_LiabilitiesFairValueAdjustment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ 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 210.9-03.13)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.(a),16(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 13
-Subparagraph 2, 3
-Article 9

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

The portion of the carrying amount of short-term borrowings outstanding as of the balance sheet date which accrues interest at a set, unchanging rate.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average interest rate of short-term debt outstanding.

+ References

+ Details

Name:	us-gaap_ShortTermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Borrowings - Short-Term Borrowings - Additional information (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) Loan	Dec. 31, 2014 USD ($) Loan	Dec. 31, 2013 USD ($)
Short-term Debt [Abstract]
Total short-term borrowings	$ 412,617,000	$ 425,077,000
Interest rate (in hundredths)	5.673%
Additional debt instrument borrowing capacity	$ 0
BancTrust [Member] \| Short Term Borrowing [Member] \| Fair Market Value Adjustment [Member]
Short-term Debt [Abstract]
Total short-term borrowings		178,000
Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Total short-term borrowings	350,000,000	356,758,000
Dallas [Member]
Short-term Debt [Abstract]
Additional debt instrument borrowing capacity	$ 1,328,000,000	$ 1,678,000,000
Dallas [Member] \| Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Number of outstanding short-term FHLB advances \| Loan	2	4
Total short-term borrowings	$ 350,000,000	$ 350,000,000
Interest rate (in hundredths)	0.31%
Weighted average remaining maturity	13 days	9 days
Weighted-average cost related to FHLB advances (in hundredths)	0.31%	0.14%
Atlanta [Member]
Short-term Debt [Abstract]
Interest expense, short-term borrowings	$ 727,000	$ 197,000	$ 6,000
Atlanta [Member] \| Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Number of outstanding short-term FHLB advances \| Loan	0	2
Weighted average remaining maturity		297 days
Interest rate (in hundredths)		3.96%
Atlanta [Member] \| Federal Home Loan Bank Advances [Member] \| Advance One [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 80,000
Interest rate (in hundredths)	6.95%
Atlanta [Member] \| Federal Home Loan Bank Advances [Member] \| Advance Two [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 6,500,000
Interest rate (in hundredths)	3.92%
Minimum [Member] \| Dallas [Member] \| Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 100,000,000	$ 50,000,000
Interest rate (in hundredths)		0.10%
Maximum [Member] \| Dallas [Member] \| Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 250,000,000	$ 100,000,000
Interest rate (in hundredths)		0.18%