Note 2 - Net Income Per Share Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income—diluted		$ 114,486	$ 76,257
Dilutive effect of share-based compensation arrangements (2)	[1]	3,916	4,017
Adjusted average common shares outstanding—diluted		219,883	221,497
Net income (loss)—diluted		$ 0.52	$ 0.34
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Average common shares outstanding - basic		215,967	214,925
Net income per share - basic		$ 0.53	$ 0.36
Net income		$ 114,486	$ 76,472
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	$ (215)
Dilutive effect of Convertible Senior Notes		0	1,854
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	701
Stock Compensation Plan [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares of common stock equivalents		170	445

[1] The following number of shares of our common stock equivalents issued under our share-based compensation arrangements were not included in the calculation of diluted net income per share because they were anti-dilutive: Three Months EndedMarch 31,(In thousands)2018 2017Shares of common stock equivalents170 445

[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 three months ended March 31, 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.