Note 3 - Securities (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Number of Temporarily Impaired Securities	614
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value	$ 648,278
Continuous Unrealized Loss Position Aggregate Losses	$ 103,152
Number of Temporarily Impaired Securities Greater than Twelve Months	289
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value	$ 259,070	$ 51,999
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses	64,043	2,145
Debt Securities, Available-for-Sale, Restricted	345,689	287,023
National Bank of Blacksburg [Member] | Federal Home Loan Bank of Atlanta [Member]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	645,539
Restricted Stock [Member]
Restricted Investments	$ 941	845
US Government Agencies Debt Securities [Member]
Number of Temporarily Impaired Securities	222
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value	$ 190,950
Continuous Unrealized Loss Position Aggregate Losses	42,303
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value	190,950	26,792
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses	$ 42,303	1,180
US States and Political Subdivisions Debt Securities [Member]
Number of Temporarily Impaired Securities	58
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value	$ 52,134
Continuous Unrealized Loss Position Aggregate Losses	19,645
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value	52,134
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses	$ 19,645
Commercial Mortgage-Backed Securities [Member]
Number of Temporarily Impaired Securities	8
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value	$ 15,165
Continuous Unrealized Loss Position Aggregate Losses	1,913
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value	15,165	4,665
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses	$ 1,913	172
Corporate Debt Securities [Member]
Number of Temporarily Impaired Securities	1
Available-for-sale and Held to Maturity Securities Continuous Unrealized Loss Position Fair Value	$ 821
Continuous Unrealized Loss Position Aggregate Losses	182
Continuous Unrealized Loss Position Twelve Months or Longer Fair Value	821	0
Continuous Unrealized Loss Position 12 Months or Longer Aggregate Losses	182	0
Securities Called [Member]
Debt Securities, Available-for-Sale, Realized Gain (Loss), Total	$ 0	$ 6