Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Computation of basic and diluted earnings per share
Numerator for basic and diluted earnings per share - net income (loss) attributable to common stockholders	$ (8,508)		$ 54,735		$ 46,551		$ 94,037
Denominator for basic earnings per share - weighted average shares	273,091,000		213,498,000		266,602,000		206,612,000
Effect of dilutive securities:
Employee stock options	283,000		261,000		0		242,000
Non-vested restricted shares	370,000		299,000		0		290,000
Convertible senior unsecured notes	2,737,000		1,080,000		0		1,093,000
Dilutive potential common shares	3,390,000		1,640,000		0		1,625,000
Denominator for diluted earnings per share - adjusted weighted average shares	276,481,000		215,138,000		266,602,000		208,237,000
Basic earnings per share	$ (0.03)	[1]	$ 0.26	[1]	$ 0.17	[1]	$ 0.46	[1]
Diluted earnings per share	$ (0.03)	[1]	$ 0.25	[1]	$ 0.17	[1]	$ 0.45	[1]
Earnings Per Share (Textual) [Abstract]
Securities Excluded From Computation Of Diluted Earnings Per Share	0		354,000		0		366,000

[1] Amounts may not sum due to rounding