Note 12 - Minimum Regulatory Capital Requirement - Minimum Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016
Total capital (to risk weighted assets), actual, amount	$ 198,468		$ 191,006
Total capital (to risk weighted assets), actual, ratio	24.542%		26.575%
Total capital (to risk weighted assets), minimum capital requirement, amount	$ 74,804	[1]	$ 57,499
Total capital (to risk weighted assets), minimum capital requirement, ratio	9.25%	[1]	8.625%
Total capital (to risk weighted assets), minimum to be well capitalized, amount
Total capital (to risk weighted assets), minimum to be well capitalized, ratio
Tier 1 capital (to risk weighted assets), actual, amount	$ 190,543		$ 182,706
Tier 1 capital (to risk weighted assets), actual, ratio	23.562%		25.42%
Tier 1 capital (to risk weighted assets), minimum capital requirement, amount	$ 58,630	[1]	$ 43,124
Tier 1 capital (to risk weighted assets), minimum capital requirement, ratio	7.25%	[1]	6.625%
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, ratio
Common equity tier 1 capital (to risk weighted assets), actual, amount	$ 190,543		$ 182,706
Common equity tier 1 capital (to risk weighted assets), actual, ratio	23.562%		25.42%
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, amount	$ 46,500	[1]	$ 32,343
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, ratio	5.75%	[1]	5.125%
Common equity tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount
Common equity tier 1 capital (to risk weighted assets), minimum to be well capitalized, ratio
Tier 1 capital (to average assets), actual, amount	$ 190,543		$ 182,706
Tier 1 capital (to average assets), actual, ratio	15.424%		15.121%
Tier 1 capital (to average assets), minimum capital requirement, amount	$ 49,413	[1]	$ 48,333
Tier 1 capital (to average assets), minimum capital requirement, ratio	4.00%	[1]	4.00%
Tier 1 capital (to average assets), minimum to be well capitalized, amount
Tier 1 capital (to average assets), minimum to be well capitalized, ratio
National Bank of Blacksburg [Member]
Total capital (to risk weighted assets), actual, amount	$ 195,903		$ 188,095
Total capital (to risk weighted assets), actual, ratio	24.316%		26.296%
Total capital (to risk weighted assets), minimum capital requirement, amount	$ 74,523	[1]	$ 57,224
Total capital (to risk weighted assets), minimum capital requirement, ratio	9.25%	[1]	8.625%
Total capital (to risk weighted assets), minimum to be well capitalized, amount	$ 80,566		$ 71,529
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	$ 187,978		$ 179,795
Tier 1 capital (to risk weighted assets), actual, ratio	23.332%		25.136%
Tier 1 capital (to risk weighted assets), minimum capital requirement, amount	$ 58,410	[1]	$ 42,918
Tier 1 capital (to risk weighted assets), minimum capital requirement, ratio	7.25%	[1]	6.625%
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount	$ 64,452		$ 57,224
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	$ 187,978		$ 179,795
Common equity tier 1 capital (to risk weighted assets), actual, ratio	23.332%		25.136%
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, amount	$ 46,325	[1]	$ 32,188
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, ratio	5.75%	[1]	5.125%
Common equity tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount	$ 52,368		$ 46,494
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	$ 187,978		$ 179,795
Tier 1 capital (to average assets), actual, ratio	15.254%		14.964%
Tier 1 capital (to average assets), minimum capital requirement, amount	$ 49,293	[1]	$ 48,060
Tier 1 capital (to average assets), minimum capital requirement, ratio	4.00%	[1]	4.00%
Tier 1 capital (to average assets), minimum to be well capitalized, amount	$ 61,616		$ 60,075
Tier 1 capital (to average assets), minimum to be well capitalized, ratio	5.00%		5.00%

[1] Except with regard to the Company's and 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 Company's and 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.