Allowance for Probable Loan Losses (Impaired Loans) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Interest Recognized
Total trouble debt restructuring	$ 7,989		$ 7,989	$ 8,158
Period of charge off for past due unsecured commercial loans	90 days		90 days
Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	$ 3,809	$ 1,805	$ 3,809	1,698
Total impaired loans with no related allowance	19,898	65,399	19,898	22,202
Unpaid principal balance:
Total impaired loans with an allowance recorded	4,472		4,472	2,330
Total impaired loans with no related allowance recorded	21,106	184	21,106	23,284
Related Allowance	1,699		1,699	772
Average recorded investment:
Total impaired loans with an allowance recorded	3,817	1,747	3,824	1,882
Total impaired loans with no related allowance recorded	42,125	64,903	48,909	65,192
Interest Recognized
Total impaired loans with no related allowance recorded	93	94	182	368
Commercial
Interest Recognized
Total trouble debt restructuring	34		34	35
Commercial \| Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	1,309	1,661	1,309	1,563
Total impaired loans with no related allowance	7,163	16,738	7,163	7,616
Unpaid principal balance:
Total impaired loans with an allowance recorded	1,904		1,904	2,161
Total impaired loans with no related allowance recorded	7,294	1	7,294	7,730
Related Allowance	648		648	656
Average recorded investment:
Total impaired loans with an allowance recorded	1,316	1,604	1,322	1,741
Total impaired loans with no related allowance recorded	16,788	16,594	17,078	16,194
Interest Recognized
Total impaired loans with no related allowance recorded	1	1	1	3
Commercial Real Estate:Other Construction and Land Development \| Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	131	144	131	135
Total impaired loans with no related allowance	1,793	2,216	1,793	1,957
Unpaid principal balance:
Total impaired loans with an allowance recorded	169		169	169
Total impaired loans with no related allowance recorded	2,078		2,078	2,205
Related Allowance	116		116	116
Average recorded investment:
Total impaired loans with an allowance recorded	132	143	133	141
Total impaired loans with no related allowance recorded	1,792	2,148	1,813	2,151
Commercial Real Estate: Farmland and Commercial \| Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	2,369		2,369
Total impaired loans with no related allowance	1,792	36,686	1,792	3,509
Unpaid principal balance:
Total impaired loans with an allowance recorded	2,399		2,399
Total impaired loans with no related allowance recorded	2,382		2,382	4,031
Related Allowance	935		935
Average recorded investment:
Total impaired loans with an allowance recorded	2,369		2,369
Total impaired loans with no related allowance recorded	14,203	36,790	20,551	36,632
Commercial Real Estate: Multifamily \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	505	568	505	507
Unpaid principal balance:
Total impaired loans with no related allowance recorded	536		536	538
Average recorded investment:
Total impaired loans with no related allowance recorded	507	664	507	565
Residential First Lien
Interest Recognized
Total trouble debt restructuring	5,905		5,905	5,947
Residential First Lien \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	6,297	6,864	6,297	6,244
Unpaid principal balance:
Total impaired loans with no related allowance recorded	6,459	152	6,459	6,386
Average recorded investment:
Total impaired loans with no related allowance recorded	6,480	6,426	6,579	7,136
Interest Recognized
Total impaired loans with no related allowance recorded	78	76	153	305
Residential Junior Lien
Interest Recognized
Total trouble debt restructuring	734		734	730
Residential Junior Lien \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	1,023	811	1,023	901
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,032	22	1,032	911
Average recorded investment:
Total impaired loans with no related allowance recorded	1,028	803	1,033	976
Interest Recognized
Total impaired loans with no related allowance recorded	11	12	22	44
Consumer
Interest Recognized
Total trouble debt restructuring	1,037		1,037	1,153
Consumer \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	1,046	1,179	1,046	1,175
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,046	2	1,046	1,190
Average recorded investment:
Total impaired loans with no related allowance recorded	1,046	1,145	1,063	1,211
Interest Recognized
Total impaired loans with no related allowance recorded		1		2
Foreign
Interest Recognized
Total trouble debt restructuring	279		279	293
Foreign \| Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	279	337	279	293
Unpaid principal balance:
Total impaired loans with no related allowance recorded	279	7	279	293
Average recorded investment:
Total impaired loans with no related allowance recorded	281	333	285	327
Interest Recognized
Total impaired loans with no related allowance recorded	$ 3	$ 4	$ 6	$ 14

Amount of financing receivable modified as troubled debt restructuring.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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