Note 12 - Regulatory Matters (Details Textual) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended	50 Months Ended
	Apr. 11, 2019	Jan. 17, 2019	Mar. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Apr. 19, 2016	Jan. 30, 2015	Dec. 31, 2009
Preferred Securities of Subsidiary Trust			$ 44.3	$ 44.3	$ 44.1
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								$ 15,000.0
Capital Conservation Buffer					2.50%
Common Stock, Dividends, Per Share, Declared		$ 0.26
Dividends Payable, Date to be Paid		Mar. 20, 2019
Stock Repurchase Program, Authorized Amount							$ 20.0
Stock Repurchase Program Additional Authorized Amount						$ 15.0
Stock Repurchased During Period, Shares			119,120	1,275,444
Stock Repurchased During Period, Value			$ 3.6	$ 29.0
Treasury Stock Acquired, Average Cost Per Share			$ 30.23	$ 22.77
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.26
Dividends Payable, Date to be Paid	Jun. 19, 2019