Note 1 - Interim Financial Statements - Reconciliation of Earnings (Loss) and the Weighted Average Number of Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net income available to the Company's common shareholders		$ 131,861	$ 191,854	$ 197,039	$ 321,012
Earnings attributable to participating securities		(647)	(1,067)	(1,070)	(1,701)
Net income available to the Company’s common shareholders for basic earnings per share		131,214	190,787	195,969	319,311
Distributions on convertible units		259	28	29	47
Net income available to the Company’s common shareholders for diluted earnings per share		$ 131,473	$ 190,815	$ 195,998	$ 319,358
Weighted average common shares outstanding – basic (in shares)		423,650	417,748	423,516	415,189
Effect of dilutive securities (a):
Equity awards (in shares)	[1]	432	1,457	505	1,450
Assumed conversion of convertible units (in shares)	[1]	862	97	63	93
Weighted average common shares outstanding – diluted (in shares)		424,944	419,302	424,084	416,732
-Basic (in dollars per share)		$ 0.31	$ 0.46	$ 0.46	$ 0.77
-Diluted (in dollars per share)		$ 0.31	$ 0.46	$ 0.46	$ 0.77

[1] The effect of the assumed conversion of certain convertible units had an anti-dilutive effect upon the calculation of Income from continuing operations per share. Accordingly, the impact of such conversions has not been included in the determination of diluted earnings per share calculations. Additionally, there were 3,445,600 and 5,235,280 stock options that were not dilutive as of March 31, 2017 and 2016, respectively.