Allowance for Probable Loan Losses (Impaired Loans) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2016	Dec. 31, 2015
Interest Recognized
Total trouble debt restructuring	$ 16,070	$ 15,719
Period of charge off for past due unsecured commercial loans	90 days
Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	$ 10,299	8,785
Total impaired loans with no related allowance	33,673	51,663
Unpaid principal balance:
Total impaired loans with an allowance recorded	10,532	9,233
Total impaired loans with no related allowance recorded	61,983	64,788
Related Allowance	3,723	2,206
Average recorded investment:
Total impaired loans with an allowance recorded	10,302	9,694
Total impaired loans with no related allowance recorded	44,438	53,575
Interest Recognized
Total impaired loans with an allowance recorded	26	92
Total impaired loans with no related allowance recorded	116	441
Commercial
Interest Recognized
Total trouble debt restructuring	2,419	2,419
Commercial \| Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	4,018	4,016
Total impaired loans with no related allowance	10,840	26,930
Unpaid principal balance:
Total impaired loans with an allowance recorded	4,158	4,156
Total impaired loans with no related allowance recorded	37,845	38,845
Related Allowance	2,347	1,704
Average recorded investment:
Total impaired loans with an allowance recorded	4,017	3,758
Total impaired loans with no related allowance recorded	21,051	30,847
Interest Recognized
Total impaired loans with no related allowance recorded	1	4
Commercial Real Estate: Other Construction and Land Development
Interest Recognized
Total trouble debt restructuring	2,553	2,553
Commercial Real Estate: Other Construction and Land Development \| Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	165	167
Total impaired loans with no related allowance	5,800	6,054
Unpaid principal balance:
Total impaired loans with an allowance recorded	169	169
Total impaired loans with no related allowance recorded	5,801	6,204
Related Allowance	116	100
Average recorded investment:
Total impaired loans with an allowance recorded	165	893
Total impaired loans with no related allowance recorded	6,296	6,455
Interest Recognized
Total impaired loans with no related allowance recorded	25	85
Commercial Real Estate: Farmland & Commercial
Interest Recognized
Total trouble debt restructuring	2,847	2,853
Commercial Real Estate: Farmland & Commercial \| Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	6,116	4,003
Total impaired loans with no related allowance	7,524	9,803
Unpaid principal balance:
Total impaired loans with an allowance recorded	6,205	4,309
Total impaired loans with no related allowance recorded	8,730	10,717
Related Allowance	1,260	202
Average recorded investment:
Total impaired loans with an allowance recorded	6,120	4,444
Total impaired loans with no related allowance recorded	7,590	7,258
Interest Recognized
Total impaired loans with an allowance recorded	26	92
Commercial Real Estate: Multifamily \| Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance		599
Total impaired loans with no related allowance	164	178
Unpaid principal balance:
Total impaired loans with an allowance recorded		599
Total impaired loans with no related allowance recorded	164	178
Related Allowance		200
Average recorded investment:
Total impaired loans with an allowance recorded		599
Total impaired loans with no related allowance recorded	168	205
Residential First Lien
Interest Recognized
Total trouble debt restructuring	5,709	5,316
Residential First Lien \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	6,358	5,699
Unpaid principal balance:
Total impaired loans with no related allowance recorded	6,433	5,822
Average recorded investment:
Total impaired loans with no related allowance recorded	6,340	5,853
Interest Recognized
Total impaired loans with no related allowance recorded	71	264
Residential Junior Lien
Interest Recognized
Total trouble debt restructuring	988	929
Residential Junior Lien \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	1,032	950
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,055	972
Average recorded investment:
Total impaired loans with no related allowance recorded	1,036	1,182
Interest Recognized
Total impaired loans with no related allowance recorded	15	68
Consumer
Interest Recognized
Total trouble debt restructuring	1,174	1,263
Consumer \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	1,210	1,297
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,210	1,298
Average recorded investment:
Total impaired loans with no related allowance recorded	1,210	1,227
Interest Recognized
Total impaired loans with no related allowance recorded		3
Foreign
Interest Recognized
Total trouble debt restructuring	380	386
Foreign \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	745	752
Unpaid principal balance:
Total impaired loans with no related allowance recorded	745	752
Average recorded investment:
Total impaired loans with no related allowance recorded	747	548
Interest Recognized
Total impaired loans with no related allowance recorded	$ 4	$ 17

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

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Amount of allowance for credit losses related to recorded investment.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5258-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section 50
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5258-111524

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Threshold period past due for financing receivable to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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