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Allowance for Probable Loan Losses (Impaired Loans) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Interest Recognized
Total trouble debt restructuring	$ 24,823		$ 24,823		$ 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	7,402		$ 7,402		8,785
Total impaired loans with no related allowance	40,189		40,189		51,663
Unpaid principal balance:
Total impaired loans with an allowance recorded	8,633		8,633		9,233
Total impaired loans with no related allowance recorded	68,367		68,367		64,788
Related Allowance	1,396		1,396		2,206
Average recorded investment:
Total impaired loans with an allowance recorded	7,442	$ 14,934	9,040	$ 20,816	33,286
Total impaired loans with no related allowance recorded	33,532	42,643	36,577	43,580	42,643
Interest Recognized
Total impaired loans with an allowance recorded	24	23	73	69	92
Total impaired loans with no related allowance recorded	109	106	338	318	106
Commercial
Interest Recognized
Total trouble debt restructuring	11,754		11,754		2,419
Commercial | Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	2,214		2,214		4,016
Total impaired loans with no related allowance	19,717		19,717		26,930
Unpaid principal balance:
Total impaired loans with an allowance recorded	2,293		2,293		4,156
Total impaired loans with no related allowance recorded	46,729		46,729		38,845
Related Allowance	734		734		1,704
Average recorded investment:
Total impaired loans with an allowance recorded	2,247	11,247	3,239	15,634	19,313
Total impaired loans with no related allowance recorded	13,813	21,291	15,234	20,623	21,291
Interest Recognized
Total impaired loans with no related allowance recorded	1	1	3	3	1
Commercial Real Estate: Other Construction and Land Development
Interest Recognized
Total trouble debt restructuring	1,585		1,585		2,553
Commercial Real Estate: Other Construction and Land Development | Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	158		158		167
Total impaired loans with no related allowance	4,443		4,443		6,054
Unpaid principal balance:
Total impaired loans with an allowance recorded	169		169		169
Total impaired loans with no related allowance recorded	4,457		4,457		6,204
Related Allowance	116		116		100
Average recorded investment:
Total impaired loans with an allowance recorded	159	170	162	1,136	7,183
Total impaired loans with no related allowance recorded	3,924	6,045	4,927	6,561	6,045
Interest Recognized
Total impaired loans with no related allowance recorded	14	20	53	57	20
Commercial Real Estate: Farmland & Commercial
Interest Recognized
Total trouble debt restructuring	3,101		3,101		2,853
Commercial Real Estate: Farmland & Commercial | Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	5,030		5,030		4,003
Total impaired loans with no related allowance	5,716		5,716		9,803
Unpaid principal balance:
Total impaired loans with an allowance recorded	6,171		6,171		4,309
Total impaired loans with no related allowance recorded	6,751		6,751		10,717
Related Allowance	546		546		202
Average recorded investment:
Total impaired loans with an allowance recorded	5,036	3,517	5,639	4,046	6,790
Total impaired loans with no related allowance recorded	5,513	6,203	6,469	7,253	6,203
Interest Recognized
Total impaired loans with an allowance recorded	24	23	73	69	92
Total impaired loans with no related allowance recorded	3		10
Commercial Real Estate: Multifamily | Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance					599
Total impaired loans with no related allowance	571		571		178
Unpaid principal balance:
Total impaired loans with an allowance recorded					599
Total impaired loans with no related allowance recorded	576		576		178
Related Allowance					200
Average recorded investment:
Total impaired loans with no related allowance recorded	577	819	349	832	819
Interest Recognized
Total impaired loans with no related allowance recorded				1
Residential First Lien
Interest Recognized
Total trouble debt restructuring	5,960		5,960		5,316
Residential First Lien | Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	6,752		6,752		5,699
Unpaid principal balance:
Total impaired loans with no related allowance recorded	6,840		6,840		5,822
Average recorded investment:
Total impaired loans with no related allowance recorded	6,712	5,315	6,644	5,375	5,315
Interest Recognized
Total impaired loans with no related allowance recorded	75	65	220	188	65
Residential Junior Lien
Interest Recognized
Total trouble debt restructuring	830		830		929
Residential Junior Lien | Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	1,008		1,008		950
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,032		1,032		972
Average recorded investment:
Total impaired loans with no related allowance recorded	1,012	1,075	1,011	1,255	1,075
Interest Recognized
Total impaired loans with no related allowance recorded	12	15	39	54	15
Consumer
Interest Recognized
Total trouble debt restructuring	1,227		1,227		1,263
Consumer | Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	1,230		1,230		1,297
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,230		1,230		1,298
Average recorded investment:
Total impaired loans with no related allowance recorded	1,229	1,263	1,191	1,201	1,263
Interest Recognized
Total impaired loans with no related allowance recorded		1	1	2	1
Foreign
Interest Recognized
Total trouble debt restructuring	366		366		386
Foreign | Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	752		752		752
Unpaid principal balance:
Total impaired loans with no related allowance recorded	752		752		752
Average recorded investment:
Total impaired loans with no related allowance recorded	752	632	752	480	632
Interest Recognized
Total impaired loans with no related allowance recorded	$ 4	$ 4	$ 12	$ 13	$ 4

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- Definition

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

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