Note 11 - Minimum Regulatory Capital Requirement - Minimum Capital Requirements (Details) - National Bank of Blacksburg [Member] $ in Thousands		Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Total capital (to risk weighted assets), actual, amount		$ 185,937	$ 188,946
Total capital (to risk weighted assets), actual, ratio		0.19943	0.23128
Total capital (to risk weighted assets), minimum capital requirement, amount	[1]	$ 97,898	$ 85,781
Total capital (to risk weighted assets), minimum capital requirement, ratio	[1]	0.10500	0.10500
Total capital (to risk weighted assets), minimum to be well capitalized, amount		$ 93,236	$ 81,696
Total capital (to risk weighted assets), minimum to be well capitalized, ratio		0.10000	0.10000
Tier 1 capital (to risk weighted assets), actual, amount		$ 177,409	$ 182,044
Tier 1 capital (to risk weighted assets), actual, ratio		0.19028	0.22283
Tier 1 capital (to risk weighted assets), minimum capital requirement, amount	[1]	$ 79,251	$ 69,442
Tier 1 capital (to risk weighted assets), minimum capital requirement, ratio	[1]	0.08500	0.08500
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount		$ 74,589	$ 65,357
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, ratio		0.08000	0.08000
Common equity tier 1 capital (to risk weighted assets), actual, amount		$ 177,409	$ 182,044
Common equity tier 1 capital (to risk weighted assets), actual, ratio		0.19028	0.22283
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, amount	[1]	$ 65,265	$ 57,187
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, ratio	[1]	7.00%	7.00%
Common equity tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount		$ 60,604	$ 53,103
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		$ 177,409	$ 182,044
Tier 1 capital (to average assets), actual, ratio		0.12105	0.14175
Tier 1 capital (to average assets), minimum capital requirement, amount	[1]	$ 58,624	$ 51,371
Tier 1 capital (to average assets), minimum capital requirement, ratio	[1]	0.04000	0.04000
Tier 1 capital (to average assets), minimum to be well capitalized, amount		$ 73,281	$ 64,213
Tier 1 capital (to average assets), minimum to be well capitalized, ratio		0.05000	0.05000

[1] Except with regard to NBB’s Tier 1 capital to average assets ratio, the minimum capital requirement includes the Basel III Capital Rules’ capital conservation buffer (2.50%) which is added to the minimum capital requirements for capital adequacy purposes. NBB’s capital conservation buffer consists 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.