Note 2 - Net Income Per Share Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Contingently Issuable Shares			0
Net income (loss)—diluted		$ 208,949	$ (27,342)	$ 323,435	$ 48,915
Dilutive effect of share-based compensation arrangements (2)	[1]	3,854	0	3,692	3,896
Adjusted average common shares outstanding—diluted		217,830	215,152	218,741	220,474
Net income (loss)—diluted		$ 0.96	$ (0.13)	$ 1.48	$ 0.22
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income (loss)—basic		$ 208,949	$ (27,342)
Net income		$ 208,949	$ (27,342)	$ 323,435	$ 49,130
Average common shares outstanding - basic		213,976	215,152	215,049	215,054
Net income per share - basic		$ 0.98	$ (0.13)	$ 1.50	$ 0.23
Convertible Debt | Convertible Senior Notes Due 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Adjustment for dilutive Convertible Senior Notes due 2019, net of tax (1)	[2]	$ 0	$ 0	$ 0	$ (215)
Dilutive effect of Convertible Senior Notes		0	0	0	922
Convertible Debt | Convertible Senior Notes Due 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of Convertible Senior Notes		0	0	0	602
Stock Compensation Plan [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares of common stock equivalents		484	5,975	351	442
Convertible Debt Securities [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares of common stock equivalents		0	509	0	0

[1] There were no dilutive shares for the three months ended June 30, 2017, as a result of our net loss for the period. The following number of shares of our common stock equivalents issued under our share-based compensation arrangements and convertible debt, if any, were not included in the calculation of diluted net income (loss) per share because they were anti-dilutive: Three Months EndedJune 30, Six Months EndedJune 30,(In thousands)2018 2017 2018 2017Shares of common stock equivalents484 5,975 351 442Shares of Convertible Senior Notes due 2017— 509 — —

[2] As applicable, includes coupon interest, amortization of discount and fees, and other changes in income that would result from the assumed conversion. Included in the six months ended June 30, 2017 is a benefit related to our adjustment of estimated accrued expense to actual amounts, resulting from the January 2017 settlement of our obligations on the remaining Convertible Senior Notes due 2019.