Note 11 - Regulatory Matters (Details Textual) - USD ($) $ / shares in Units, $ in Thousands							3 Months Ended				9 Months Ended		62 Months Ended
	Dec. 16, 2020	Sep. 16, 2020	Jun. 17, 2020	Apr. 16, 2020	Mar. 18, 2020	Jan. 16, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	May 31, 2019	Dec. 31, 2009
Preferred Securities of Subsidiary Trust							$ 45,300				$ 45,300			$ 44,800
Maximum Restricted Core Element Allowed in Tier One Capital Percent											25.00%
Maximum Level of Consolidated Aggregate Assets Allowing for Inclusion of Trust Preferred Securities in Tier One Capital																$ 15,000,000
Trust Preferred Securities Included in Tier One Capital							$ 45,300				$ 45,300			$ 44,800
Capital Conservation Buffer							2.50%				2.50%
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy to Risk Weighted Assets							0.070				0.070
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets							0.085				0.085
Capital Required for Capital Adequacy to Risk Weighted Assets							0.105				0.105
Common Stock, Dividends, Per Share, Declared (in dollars per share)				$ 0.28		$ 0.28
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)		$ 0.28	$ 0.28		$ 0.28		$ 0.28			$ 0.27	$ 0.84	$ 0.79
Stock Repurchase Program, Authorized Amount															$ 20,000
Stock Repurchased During Period, Shares (in shares)							0	0	222,385				1,600,000
Stock Repurchased During Period, Value							$ 0	$ 0	$ 6,300				$ 38,900
Treasury Stock Acquired, Average Cost Per Share (in dollars per share)									$ 28.25				$ 24.13
Stock Repurchase Program, Remaining Authorized Repurchase Amount							$ 10,100				$ 10,100
Forecast [Member]
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 0.28