Note 2 - Net Income Per Share Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income—diluted		$ 170,957	$ 114,486
Dilutive effect of share-based compensation arrangements	[1]	4,806	3,916
Adjusted average common shares outstanding—diluted		218,343	219,883
Net income (loss) per share—diluted		$ 0.78	$ 0.52
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income - basic		$ 170,957	$ 114,486
Average common shares outstanding - basic		213,537	215,967
Net income (loss) per share - basic		$ 0.80	$ 0.53
Stock Compensation Plan
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares of common stock equivalents		169	170

[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 Ended
March 31, (In thousands) 2019   2018 Shares of common stock equivalents 169
  170