Note 3 - Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income (loss) - basic	$ 126,412	$ 135,103	$ 407,226	$ 245,613
Average common shares outstanding - basic	186,741	193,176	191,357	196,120
Net income (loss) per share - basic	$ 0.68	$ 0.70	$ 2.13	$ 1.25
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income (loss)—diluted	$ 126,412	$ 135,103	$ 407,226	$ 245,613
Dilutive effect of share-based compensation arrangements	1,301	980	1,545	1,127
Adjusted average common shares outstanding—diluted	188,042	194,156	192,902	197,247
Net income (loss) per share—diluted	$ 0.67	$ 0.70	$ 2.11	$ 1.25
Stock Compensation Plan
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Shares of common stock equivalents	0	710	0	1,046