Note 9 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Jan. 12, 2016	Jul. 28, 2015
Common Stock, Dividends, Per Share, Declared (in dollars per share)	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20
Dividends, Common Stock							$ 6.9	$ 6.9
Stock Repurchase Program, Authorized Amount									$ 70.0	$ 15.0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 21.9						$ 21.9