Note 10 - Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net (loss) income	$ 55,819	$ 1,777	$ (10,554)	$ 10,779	$ (4,109)	$ (770)	$ 7,195	$ 13,690	$ 57,821	$ 16,006	$ (96,378)
Basic (in shares)									165,635	161,141	122,132
Effect of dilutive securities: Stock options, restricted shares and performance based shares (in shares)									2,054	1,703
Denominator for diluted earnings per share - adjusted weighted-average shares and assumed exercise of options, restricted shares and performance based shares (in shares)									167,689	162,844	122,132
Net income (loss) per common share - basic (in dollars per share)	$ 0.34	$ 0.01	$ (0.06)	$ 0.07	$ (0.02)		$ 0.04	$ 0.09	$ 0.35	$ 0.10	$ (0.79)
Net income (loss) per common share - diluted (in dollars per share)	$ 0.33	$ 0.01	$ (0.06)	$ 0.06	$ (0.02)		$ 0.04	$ 0.09	$ 0.34	$ 0.10	$ (0.79)