Note 3 - Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income (loss) - basic	$ 125,608	$ 140,461
Average common shares outstanding - basic	193,439	200,161
Net income (loss) per share - basic	$ 0.65	$ 0.70
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income (loss)—diluted	$ 125,608	$ 140,461
Dilutive effect of share-based compensation arrangements	1,764	1,658
Adjusted average common shares outstanding—diluted	195,203	201,819
Net income (loss) per share—diluted	$ 0.64	$ 0.70
Stock Compensation Plan
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Shares of common stock equivalents	0	132