Organization - Additional Information (Detail)		9 Months Ended
	Jul. 01, 2016	Sep. 30, 2016
Business Acquisition [Line Items]
Date of incorporation		Nov. 02, 2015
Date of merger agreement entered		Nov. 06, 2015
Grayson Bankshares, Inc.
Business Acquisition [Line Items]
Exchange ratio	1.76
Ownership percentage in newly issued shares	60.00%
Cardinal Bankshares Corporation
Business Acquisition [Line Items]
Exchange ratio	1.30
Ownership percentage in newly issued shares	40.00%