Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 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	$ 20,691,000	$ 37,269,000	$ 67,245,000	$ 131,308,000
Denominator for basic earnings per share - weighted average shares	286,020,000	224,391,000	273,148,000	212,592,000
Effect of dilutive securities:
Employee stock options	196,000	238,000	235,000	240,000
Non-vested restricted shares	567,000	301,000	417,000	293,000
Convertible senior unsecured notes	1,246,000	1,328,000	1,447,000	950,000
Dilutive potential common shares	2,009,000	1,867,000	2,099,000	1,483,000
Denominator for diluted earnings per share - adjusted weighted average shares	288,029,000	226,258,000	275,247,000	214,075,000
Basic earnings per share	$ 0.07	$ 0.17	$ 0.25	$ 0.62
Diluted earnings per share	$ 0.07	$ 0.16	$ 0.24	$ 0.61
Earnings Per Share (Textual) [Abstract]
Securities Excluded From Computation Of Diluted Earnings Per Share	0	237,000	0	0