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Allowance for Probable Loan Losses (Details 4) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Interest Recognized
Total trouble debt restructuring	$ 15,432		$ 15,432		$ 15,653
Period of charge off for past due unsecured commercial loans			90 days
Class of financing receivable
Recorded investment:
Total impaired loans with related allowance	13,970		$ 13,970		31,765
Total impaired loans with no related allowance	42,412		42,412		44,406
Unpaid principal balance:
Total impaired loans with an allowance recorded	25,735		25,735		32,232
Total impaired loans with no related allowance recorded	44,586		44,586		46,262
Related Allowance	1,756		1,756		12,221
Average recorded investment:
Total impaired loans with an allowance recorded	14,934	$ 32,525	20,816	$ 31,715	33,286
Total impaired loans with no related allowance recorded	42,643	44,599	43,580	44,532	43,202
Interest Recognized
Total impaired loans with an allowance recorded	23	23	69	69	92
Total impaired loans with no related allowance recorded	106	112	318	336	444
Commercial
Interest Recognized
Total trouble debt restructuring	2,420		2,420		2,500
Commercial | Class of financing receivable
Recorded investment:
Total impaired loans with related allowance	10,288		10,288		19,944
Total impaired loans with no related allowance	20,977		20,977		20,231
Unpaid principal balance:
Total impaired loans with an allowance recorded	21,840		21,840		20,026
Total impaired loans with no related allowance recorded	21,909		21,909		20,260
Related Allowance	1,174		1,174		9,112
Average recorded investment:
Total impaired loans with an allowance recorded	11,247	17,677	15,634	17,550	19,313
Total impaired loans with no related allowance recorded	21,291	21,265	20,623	19,557	18,563
Interest Recognized
Total impaired loans with no related allowance recorded	1	1	3	3	4
Commercial Real Estate: Other Construction and Land Development
Interest Recognized
Total trouble debt restructuring	2,553		2,553		2,254
Commercial Real Estate: Other Construction and Land Development | Class of financing receivable
Recorded investment:
Total impaired loans with related allowance	169		169		6,714
Total impaired loans with no related allowance	6,180		6,180		4,162
Unpaid principal balance:
Total impaired loans with an allowance recorded	169		169		6,949
Total impaired loans with no related allowance recorded	6,206		6,206		4,270
Related Allowance	100		100		1,890
Average recorded investment:
Total impaired loans with an allowance recorded	170	7,329	1,136	7,326	7,183
Total impaired loans with no related allowance recorded	6,045	4,192	6,561	5,121	4,882
Interest Recognized
Total impaired loans with no related allowance recorded	20	19	57	56	74
Commercial real estate: farmland and commercial
Interest Recognized
Total trouble debt restructuring	2,853		2,853		2,861
Commercial real estate: farmland and commercial | Class of financing receivable
Recorded investment:
Total impaired loans with related allowance	3,513		3,513		5,107
Total impaired loans with no related allowance	6,129		6,129		9,059
Unpaid principal balance:
Total impaired loans with an allowance recorded	3,726		3,726		5,257
Total impaired loans with no related allowance recorded	7,263		7,263		10,562
Related Allowance	482		482		1,219
Average recorded investment:
Total impaired loans with an allowance recorded	3,517	7,519	4,046	6,839	6,790
Total impaired loans with no related allowance recorded	6,203	8,418	7,253	8,643	8,664
Interest Recognized
Total impaired loans with an allowance recorded	23	23	69	69	92
Commercial real estate: multifamily
Interest Recognized
Total trouble debt restructuring	21		21
Commercial real estate: multifamily | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	812		812		835
Unpaid principal balance:
Total impaired loans with no related allowance recorded	812		812		835
Average recorded investment:
Total impaired loans with no related allowance recorded	819	256	832	270	363
Interest Recognized
Total impaired loans with no related allowance recorded			1
Residential: first lien
Interest Recognized
Total trouble debt restructuring	4,972		4,972		5,313
Residential: first lien | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	5,294		5,294		5,840
Unpaid principal balance:
Total impaired loans with no related allowance recorded	5,353		5,353		6,034
Average recorded investment:
Total impaired loans with no related allowance recorded	5,315	5,648	5,375	6,028	6,293
Interest Recognized
Total impaired loans with no related allowance recorded	65	64	188	191	273
Residential: junior lien
Interest Recognized
Total trouble debt restructuring	1,012		1,012		1,371
Residential: junior lien | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	1,028		1,028		2,895
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,050		1,050		2,915
Average recorded investment:
Total impaired loans with no related allowance recorded	1,075	2,992	1,255	3,080	3,035
Interest Recognized
Total impaired loans with no related allowance recorded	15	22	54	69	90
Consumer
Interest Recognized
Total trouble debt restructuring	1,208		1,208		1,354
Consumer | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	1,243		1,243		1,384
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,244		1,244		1,386
Average recorded investment:
Total impaired loans with no related allowance recorded	1,263	1,408	1,201	1,407	1,402
Interest Recognized
Total impaired loans with no related allowance recorded	1	1	2	3	$ 3
Foreign
Interest Recognized
Total trouble debt restructuring	393		393
Foreign | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	749		749
Unpaid principal balance:
Total impaired loans with no related allowance recorded	749		749
Average recorded investment:
Total impaired loans with no related allowance recorded	632	420	480	426
Interest Recognized
Total impaired loans with no related allowance recorded	$ 4	$ 5	$ 13	$ 14

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