Note 11 - Stockholders' Equity and Stock Incentive Plans - Dividends (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares
Dividend Declared May 2, 2017 [Member]
Dividends, record date	Jun. 15, 2017
Dividends, payment date	Jul. 15, 2017
Dividends, amount per share (in dollars per share)	$ 0.05
Dividend Declared Sept 6, 2017 [Member]
Dividends, record date	Sep. 18, 2017
Dividends, payment date	Oct. 15, 2017
Dividends, amount per share (in dollars per share)	$ 0.05
Dividend Declared Dec 7, 2017 [Member]
Dividends, record date	Dec. 28, 2017
Dividends, payment date	Jan. 15, 2018
Dividends, amount per share (in dollars per share)	$ 0.05
Dividend Declared Mar 2, 2018 [Member]
Dividends, record date	Mar. 16, 2018
Dividends, payment date	Apr. 15, 2018
Dividends, amount per share (in dollars per share)	$ 0.05
Dividend Declared June 8, 2018 [Member]
Dividends, record date	Jun. 29, 2018
Dividends, payment date	Jul. 15, 2018
Dividends, amount per share (in dollars per share)	$ 0.06
Dividend Declared Sept 14, 2018 [Member]
Dividends, record date	Sep. 28, 2018
Dividends, payment date	Oct. 15, 2018
Dividends, amount per share (in dollars per share)	$ 0.06
Dividend Declared Dec 7, 2018 [Member]
Dividends, record date	Dec. 28, 2018
Dividends, payment date	Jan. 15, 2019
Dividends, amount per share (in dollars per share)	$ 0.06
Dividend Declared Mar 4, 2019 [Member]
Dividends, record date	Mar. 15, 2019
Dividends, payment date	Apr. 15, 2019
Dividends, amount per share (in dollars per share)	$ 0.06
Dividend Declared June 7, 2019 [Member]
Dividends, record date	Jun. 17, 2019
Dividends, payment date	Jul. 15, 2019
Dividends, amount per share (in dollars per share)	$ 0.07
Dividend Declared September 17, 2019 [Member]
Dividends, record date	Sep. 27, 2019
Dividends, payment date	Oct. 15, 2019
Dividends, amount per share (in dollars per share)	$ 0.07
Dividend Declared Dec 17, 2019 [Member]
Dividends, record date	Dec. 27, 2019
Dividends, payment date	Jan. 15, 2020
Dividends, amount per share (in dollars per share)	$ 0.07