Loans and Leases Held for Investment and Allowance for Loan and Lease Losses - Summary of Risk Grades of Each Category of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 2,009,309	$ 1,850,480
Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	668,880	618,748
Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	266,424	248,904
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	818,804	739,030
Commercial Land
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	255,201	243,798
Healthcare | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	49,752	51,082
Healthcare | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	80,476	81,619
Healthcare | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	215,093	188,531
Risk Grades 1 - 4
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,839,255	1,702,491
Risk Grades 1 - 4 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	609,428	559,716
Risk Grades 1 - 4 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	261,491	247,099
Risk Grades 1 - 4 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	738,659	671,850
Risk Grades 1 - 4 | Commercial Land
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	229,677	223,826
Risk Grades 1 - 4 | Healthcare | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	38,008	38,908
Risk Grades 1 - 4 | Healthcare | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	78,138	79,814
Risk Grades 1 - 4 | Healthcare | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	185,948	161,026
Risk Grade 5
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	74,140	65,484
Risk Grade 5 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	31,060	30,770
Risk Grade 5 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	4,933	1,805
Risk Grade 5 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	26,834	23,995
Risk Grade 5 | Commercial Land
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	11,313	8,914
Risk Grade 5 | Healthcare | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,473	2,502
Risk Grade 5 | Healthcare | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,338	1,805
Risk Grade 5 | Healthcare | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	8,830	7,696
Risk Grades 6 - 8
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	95,914	82,505
Risk Grades 6 - 8 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	28,392	28,262
Risk Grades 6 - 8 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	53,311	43,185
Risk Grades 6 - 8 | Commercial Land
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	14,211	11,058
Risk Grades 6 - 8 | Healthcare | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	9,271	9,672
Risk Grades 6 - 8 | Healthcare | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	20,315	19,809
Agricultural | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	5,813	6,400
Agricultural | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	31,236	43,454
Agricultural | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	46,049	53,085
Agricultural | Commercial Land
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	255,201	243,798
Agricultural | Risk Grades 1 - 4 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	5,264	6,187
Agricultural | Risk Grades 1 - 4 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	31,236	43,454
Agricultural | Risk Grades 1 - 4 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	45,016	52,518
Agricultural | Risk Grades 1 - 4 | Commercial Land
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	229,677	223,826
Agricultural | Risk Grade 5 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	549	213
Agricultural | Risk Grade 5 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,033	567
Agricultural | Risk Grade 5 | Commercial Land
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	11,313	8,914
Agricultural | Risk Grades 6 - 8 | Commercial Land
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	14,211	11,058
Death Care Management | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	22,809	17,378
Death Care Management | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	10,153	9,874
Death Care Management | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	87,651	71,344
Death Care Management | Risk Grades 1 - 4 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	21,149	17,085
Death Care Management | Risk Grades 1 - 4 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	10,153	9,874
Death Care Management | Risk Grades 1 - 4 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	80,856	64,487
Death Care Management | Risk Grade 5 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,655	287
Death Care Management | Risk Grade 5 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	3,385	3,711
Death Care Management | Risk Grades 6 - 8 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	5	6
Death Care Management | Risk Grades 6 - 8 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	3,410	3,146
Independent Pharmacies | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	110,458	108,783
Independent Pharmacies | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,156	2,149
Independent Pharmacies | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	27,190	20,597
Independent Pharmacies | Risk Grades 1 - 4 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	96,556	93,976
Independent Pharmacies | Risk Grades 1 - 4 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,156	2,149
Independent Pharmacies | Risk Grades 1 - 4 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	17,499	12,509
Independent Pharmacies | Risk Grade 5 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	6,541	5,734
Independent Pharmacies | Risk Grade 5 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,452	2,495
Independent Pharmacies | Risk Grades 6 - 8 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	7,361	9,073
Independent Pharmacies | Risk Grades 6 - 8 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	7,239	5,593
Registered Investment Advisors | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	95,292	94,338
Registered Investment Advisors | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,586	1,232
Registered Investment Advisors | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	6,825	7,905
Registered Investment Advisors | Risk Grades 1 - 4 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	90,304	88,614
Registered Investment Advisors | Risk Grades 1 - 4 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,586	1,232
Registered Investment Advisors | Risk Grades 1 - 4 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	6,704	7,780
Registered Investment Advisors | Risk Grade 5 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,267	2,381
Registered Investment Advisors | Risk Grade 5 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	121	125
Registered Investment Advisors | Risk Grades 6 - 8 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,721	3,343
Veterinary Industry | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	45,333	45,604
Veterinary Industry | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	18,149	14,094
Veterinary Industry | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	138,129	136,721
Veterinary Industry | Risk Grades 1 - 4 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	41,671	42,175
Veterinary Industry | Risk Grades 1 - 4 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	18,149	14,094
Veterinary Industry | Risk Grades 1 - 4 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	120,974	117,879
Veterinary Industry | Risk Grade 5 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,339	1,190
Veterinary Industry | Risk Grade 5 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	4,147	4,205
Veterinary Industry | Risk Grades 6 - 8 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,323	2,239
Veterinary Industry | Risk Grades 6 - 8 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	13,008	14,637
Other Industries | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	339,423	295,163
Other Industries | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	123,668	96,482
Other Industries | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	297,867	260,847
Other Industries | Risk Grades 1 - 4 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	316,476	272,771
Other Industries | Risk Grades 1 - 4 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	121,073	96,482
Other Industries | Risk Grades 1 - 4 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	281,662	255,651
Other Industries | Risk Grade 5 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	16,236	18,463
Other Industries | Risk Grade 5 | Construction & Development
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,595
Other Industries | Risk Grade 5 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	6,866	5,196
Other Industries | Risk Grades 6 - 8 | Commercial & Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	6,711	$ 3,929
Other Industries | Risk Grades 6 - 8 | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 9,339