Loans and Allowance for Credit Losses - Impaired Loans (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	$ 29,238	$ 11,071
Impaired loans with no related allowance, unpaid contractual principal balance	32,338	12,943
Impaired loans with no related allowance, average recorded investment	20,155	12,998
Impaired loans with related allowance, recorded investment	8,051	1,985
Impaired loans with related allowance, unpaid contractual principal balance	8,116	2,012
Impaired loans with related allowance, related allowance	1,334	685
Impaired loans with related allowance, average recorded investment	5,017	5,407
Impaired loans, recorded investment	37,289	13,056
Impaired loans, unpaid contractual principal balance	40,454	14,955
Impaired loans with an allowance recorded, related allowance	1,334	685
Impaired loans, average recorded investment	25,172	18,405
Agriculture and Agriculture Real Estate (Includes Farmland) [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	326	256
Impaired loans with no related allowance, unpaid contractual principal balance	326	311
Impaired loans with no related allowance, average recorded investment	291	194
Impaired loans with related allowance, recorded investment	290
Impaired loans with related allowance, unpaid contractual principal balance	290
Impaired loans with related allowance, related allowance	160
Impaired loans with related allowance, average recorded investment	145
Impaired loans, recorded investment	616	256
Impaired loans, unpaid contractual principal balance	616	311
Impaired loans, average recorded investment	436	194
Real Estate [Member] \| Construction, Land Development and Other Land Loans [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	269	993
Impaired loans with no related allowance, unpaid contractual principal balance	270	995
Impaired loans with no related allowance, average recorded investment	631	788
Impaired loans with related allowance, recorded investment	390	391
Impaired loans with related allowance, unpaid contractual principal balance	390	391
Impaired loans with related allowance, related allowance	58	58
Impaired loans with related allowance, average recorded investment	391	195
Impaired loans, recorded investment	659	1,384
Impaired loans, unpaid contractual principal balance	660	1,386
Impaired loans, average recorded investment	1,022	983
Real Estate [Member] \| 1-4 Family Residential (Includes Home Equity) [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	10,035	4,177
Impaired loans with no related allowance, unpaid contractual principal balance	10,747	4,903
Impaired loans with no related allowance, average recorded investment	7,106	4,048
Impaired loans with related allowance, recorded investment	5,243	266
Impaired loans with related allowance, unpaid contractual principal balance	5,272	289
Impaired loans with related allowance, related allowance	504	56
Impaired loans with related allowance, average recorded investment	2,754	729
Impaired loans, recorded investment	15,278	4,443
Impaired loans, unpaid contractual principal balance	16,019	5,192
Impaired loans, average recorded investment	9,860	4,777
Real Estate [Member] \| Commercial Real Estate (Includes Multi-Family Residential) [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	3,162	2,727
Impaired loans with no related allowance, unpaid contractual principal balance	3,341	2,848
Impaired loans with no related allowance, average recorded investment	2,945	2,475
Impaired loans with related allowance, recorded investment	973
Impaired loans with related allowance, unpaid contractual principal balance	993
Impaired loans with related allowance, related allowance	283
Impaired loans with related allowance, average recorded investment	486	743
Impaired loans, recorded investment	4,135	2,727
Impaired loans, unpaid contractual principal balance	4,334	2,848
Impaired loans, average recorded investment	3,431	3,218
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	15,406	2,870
Impaired loans with no related allowance, unpaid contractual principal balance	17,610	3,810
Impaired loans with no related allowance, average recorded investment	9,138	5,358
Impaired loans with related allowance, recorded investment	1,155	1,328
Impaired loans with related allowance, unpaid contractual principal balance	1,171	1,332
Impaired loans with related allowance, related allowance	329	571
Impaired loans with related allowance, average recorded investment	1,241	3,740
Impaired loans, recorded investment	16,561	4,198
Impaired loans, unpaid contractual principal balance	18,781	5,142
Impaired loans, average recorded investment	10,379	9,098
Consumer and Other [Member]
Financing Receivable Impaired [Line Items]
Impaired loans with no related allowance, recorded investment	40	48
Impaired loans with no related allowance, unpaid contractual principal balance	44	76
Impaired loans with no related allowance, average recorded investment	44	135
Impaired loans, recorded investment	40	48
Impaired loans, unpaid contractual principal balance	44	76
Impaired loans, average recorded investment	$ 44	$ 135

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