Business Combination - Summary of impact of Certain Acquisition Accounting Adjustments (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Business Acquisition, Pro Forma Information [Line Items]
Net impact to income before income taxes		$ 1,143	$ 811	$ 2,517	$ 513
Virginia Commonwealth Bank
Business Acquisition, Pro Forma Information [Line Items]
Loans	[1]	547		1,051
Core deposit intangible	[2]	(203)		(414)
Time deposits	[3]	42		110
Depreciation	[4]	(10)		(20)
Net impact to income before income taxes		$ 376		$ 727

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

[2] CDI amortization is included in other expense 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.