Allowance for Probable Loan Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Allowance for probable loan losses
Balance at the beginning of the period	$ 64,828	$ 70,161
Losses charged to allowance	(2,687)	(2,844)
Recoveries credited to allowance	1,733	1,013
Net (losses) gains charged to allowance	(954)	(1,831)
Provision (credit) charged to operations	2,377us-gaap_ProvisionForLoanAndLeaseLosses	2,078us-gaap_ProvisionForLoanAndLeaseLosses
Balance at the end of the period	66,251	70,408
Commercial
Allowance for probable loan losses
Balance at the beginning of the period	22,352	22,433
Losses charged to allowance	(2,309)	(2,481)
Recoveries credited to allowance	796	796
Net (losses) gains charged to allowance	(1,513)	(1,685)
Provision (credit) charged to operations	2,680	7,175
Balance at the end of the period	23,519	27,923
Commercial real estate: other construction and land development
Allowance for probable loan losses
Balance at the beginning of the period	12,955	12,541
Recoveries credited to allowance	1	31
Net (losses) gains charged to allowance	1	31
Provision (credit) charged to operations	1,413	903
Balance at the end of the period	14,369	13,475
Commercial real estate: farmland and commercial
Allowance for probable loan losses
Balance at the beginning of the period	18,683	24,467
Losses charged to allowance	(17)
Recoveries credited to allowance	806	23
Net (losses) gains charged to allowance	789	23
Provision (credit) charged to operations	(1,496)	(5,556)
Balance at the end of the period	17,976	18,934
Commercial real estate: multifamily
Allowance for probable loan losses
Balance at the beginning of the period	846	776
Provision (credit) charged to operations	(6)	43
Balance at the end of the period	840	819
Residential: first lien
Allowance for probable loan losses
Balance at the beginning of the period	3,589	3,812
Losses charged to allowance	(90)	(27)
Recoveries credited to allowance	14	4
Net (losses) gains charged to allowance	(76)	(23)
Provision (credit) charged to operations	60	(265)
Balance at the end of the period	3,573	3,524
Residential: junior lien
Allowance for probable loan losses
Balance at the beginning of the period	4,683	4,249
Losses charged to allowance	(97)	(146)
Recoveries credited to allowance	106	33
Net (losses) gains charged to allowance	9	(113)
Provision (credit) charged to operations	(431)	(168)
Balance at the end of the period	4,261	3,968
Consumer Loan
Allowance for probable loan losses
Balance at the beginning of the period	660	750
Losses charged to allowance	(174)	(187)
Recoveries credited to allowance	6	80
Net (losses) gains charged to allowance	(168)	(107)
Provision (credit) charged to operations	152	105
Balance at the end of the period	644	748
Foreign
Allowance for probable loan losses
Balance at the beginning of the period	1,060	1,133
Losses charged to allowance		(3)
Recoveries credited to allowance	4	46
Net (losses) gains charged to allowance	4	43
Provision (credit) charged to operations	5	(159)
Balance at the end of the period	$ 1,069	$ 1,017

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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- Definition

Amount, after recoveries, of loans and leases that have been written-off.

+ References

No definition available.

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- Definition

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

+ 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 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

-Section 03

-Paragraph 7

-Subparagraph d

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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 to estimated loss from loan and lease transactions.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

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