Summary of Loans Classified as Past Due in Excess of Thirty Days or More and Loans Classified as Non-Accrual (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days	$ 4,755	$ 4,785
Past Due 90 Days Or More and Still Accruing	805	285
Non- Accrual	13,572	5,674
Total Past Due and Non- Accrual	19,132	10,744
Total Loans	1,748,483	1,225,306
Real Estate-residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days		2,656
Past Due 90 Days Or More and Still Accruing		176
Non- Accrual		2,692
Total Past Due and Non- Accrual		5,524
Total Loans		385,099
Residential secured loans including multifamily and farmland
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days	3,060
Past Due 90 Days Or More and Still Accruing	275
Non- Accrual	6,041
Total Past Due and Non- Accrual	9,376
Total Loans	529,515
Lease financing receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days	0	0
Past Due 90 Days Or More and Still Accruing	0	0
Non- Accrual	0	0
Total Past Due and Non- Accrual	0	0
Total Loans	2,659	2,450
Obligations of states and subdivisions
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days	0	0
Past Due 90 Days Or More and Still Accruing	0	0
Non- Accrual	0	0
Total Past Due and Non- Accrual	0	0
Total Loans	16,374	3,109
Real Estate-construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days	267	192
Past Due 90 Days Or More and Still Accruing	15	27
Non- Accrual	235	92
Total Past Due and Non- Accrual	517	311
Total Loans	251,240	183,328
Real Estate-non farm non residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days	935	1,487
Past Due 90 Days Or More and Still Accruing	447	82
Non- Accrual	6,059	1,724
Total Past Due and Non- Accrual	7,441	3,293
Total Loans	654,040	467,484
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days	222	393
Past Due 90 Days Or More and Still Accruing	30	0
Non- Accrual	1,121	1,120
Total Past Due and Non- Accrual	1,373	1,513
Total Loans	246,401	165,780
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due 30 to 89 Days	271	57
Past Due 90 Days Or More and Still Accruing	38	0
Non- Accrual	116	46
Total Past Due and Non- Accrual	425	103
Total Loans	$ 48,254	$ 18,056