Note 8 - Shareholders' Equity - Changes in Shareholders' Equity (Details) (Parentheticals)	6 Months Ended
	Jun. 30, 2018 $ / shares
Cash dividends paid, per share (in dollars per share)	$ 0.37
Parent [Member]
Cash dividends paid, per share (in dollars per share)
Noncontrolling Interest [Member]
Cash dividends paid, per share (in dollars per share)