Business Combination - Summary of impact of Certain Acquisition Accounting Adjustments (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition, Pro Forma Information [Line Items]
Net impact to income before income taxes		$ 1,224	$ 1,015	$ 3,741	$ 1,528
Virginia Commonwealth Bank
Business Acquisition, Pro Forma Information [Line Items]
Loans	[1]	357		1,408
Core deposit intangible	[2]	(196)		(610)
Time deposits	[3]	40		150
Depreciation	[4]	(10)		(30)
Net impact to income before income taxes		$ 191		$ 918

[1] Loan discount accretion is included in loan interest income, including fees, in the consolidated statements of operations.

[2] Core deposit intangible amortization is included in noninterest expense in the consolidated statements of operations.

[3] Time deposit premium amortization is included in deposits in interest expense in the consolidated statements of operations.

[4] Depreciation on the fair value adjustment of fixed assets is included in occupancy expense in noninterest expense in the consolidated statements of operations.