Earnings Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Computation of basic and diluted earnings per share
Numerator for basic and diluted earnings per share - net income (loss) attributable to common stockholders	$ 36,607		$ (4,563)		$ 129,826		$ 66,893
Denominator for basic earnings per share - weighted average shares	177,272,000		125,298,000		169,636,000		124,132,000
Effect of dilutive securities:
Employee stock options	172,000		0		180,000		112,000
Non-vested restricted shares	258,000		0		241,000		416,000
Convertible senior unsecured notes	147,000		0		244,000		0
Dilutive potential common shares	577,000		0		665,000		528,000
Denominator for diluted earnings per share - adjusted weighted average shares	177,849,000		125,298,000		170,301,000		124,660,000
Basic earnings per share	$ 0.21	[1]	$ (0.04)	[1]	$ 0.77	[1]	$ 0.54	[1]
Diluted earnings per share	$ 0.21	[1]	$ (0.04)	[1]	$ 0.76	[1]	$ 0.54	[1]
Earnings Per Share (Textual) [Abstract]
Securities Excluded From Computation Of Diluted Earnings Per Share	0		381,000		0		381,000

[1] Amounts may not sum due to rounding