Note 11 - Minimum Regulatory Capital Requirement - Minimum Capital Requirements (Details) - National Bank of Blacksburg [Member] - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Total capital (to risk weighted assets), actual, amount		$ 202,238	$ 195,903
Total capital (to risk weighted assets), actual, ratio		24.764%	24.316%
Total capital (to risk weighted assets), minimum capital requirement, amount	[1]	$ 80,645	$ 74,523
Total capital (to risk weighted assets), minimum capital requirement, ratio	[1]	9.875%	9.25%
Total capital (to risk weighted assets), minimum to be well capitalized, amount		$ 81,666	$ 80,566
Total capital (to risk weighted assets), minimum to be well capitalized, ratio		10.00%	10.00%
Tier 1 capital (to risk weighted assets), actual, amount		$ 194,823	$ 187,978
Tier 1 capital (to risk weighted assets), actual, ratio		23.856%	23.332%
Tier 1 capital (to risk weighted assets), minimum capital requirement, amount	[1]	$ 64,312	$ 58,410
Tier 1 capital (to risk weighted assets), minimum capital requirement, ratio	[1]	7.875%	7.25%
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount		$ 65,333	$ 64,452
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, ratio		8.00%	8.00%
Common equity tier 1 capital (to risk weighted assets), actual, amount		$ 194,823	$ 187,978
Common equity tier 1 capital (to risk weighted assets), actual, ratio		23.856%	23.332%
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, amount	[1]	$ 52,062	$ 46,325
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, ratio	[1]	6.375%	5.75%
Common equity tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount		$ 53,083	$ 52,368
Common equity tier 1 capital (to risk weighted assets), minimum to be well capitalized, ratio		6.50%	6.50%
Tier 1 capital (to average assets), actual, amount		$ 194,823	$ 187,978
Tier 1 capital (to average assets), actual, ratio		15.788%	15.254%
Tier 1 capital (to average assets), minimum capital requirement, amount		$ 49,359	$ 49,293
Tier 1 capital (to average assets), minimum capital requirement, ratio		4.00%	4.00%
Tier 1 capital (to average assets), minimum to be well capitalized, amount		$ 61,699	$ 61,616
Tier 1 capital (to average assets), minimum to be well capitalized, ratio		5.00%	5.00%

[1] Except with regard to the Bank's Tier 1 capital to average assets ratio, the minimum capital requirement includes the current phased-in portion of the Basel III Capital Rules capital conservation buffer (1.25%) which is added to the minimum capital requirements for capital adequacy purposes. The capital conservation buffer is being phased in through four equal annual installments of .0625% from 2016 to 2019, with full implementation in January 2019 (2.5%). The Bank's capital conservation buffer must consist of additional CET1 above regulatory minimum requirement. Failure to maintain the prescribed levels would result in limitations on capital distributions and discretionary bonuses to executives.