Note 4 - Earnings Per Common Share - Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Numerator:
Net income	$ 10,331	$ 8,214	$ 82,070
Denominator:
Basic earnings per common share - weighted-average shares (in shares)	54,572	54,426
Effect of dilutive stock options (in shares)	523	312
Diluted earnings per common share - weighted-average shares and assumed conversions (in shares)	55,095	54,738
Basic earnings per common share (in dollars per share)	$ 0.19	$ 0.15
Diluted earnings per common share (in dollars per share)	$ 0.19	$ 0.15