Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Computation of basic and diluted earnings per share
Numerator for basic and diluted earnings per share - net income (loss) attributable to common stockholders	$ 136,255,000	$ 20,691,000	$ 258,107,000	$ 67,245,000
Denominator for basic earnings per share - weighted average shares	311,117,000	286,020,000	299,137,000	273,148,000
Effect of dilutive securities:
Employee stock options	202,000	196,000	181,000	235,000
Non-vested restricted shares	505,000	567,000	506,000	417,000
Convertible senior unsecured notes	988,000	1,246,000	821,000	1,447,000
Dilutive potential common shares	1,695,000	2,009,000	1,508,000	2,099,000
Denominator for diluted earnings per share - adjusted weighted average shares	312,812,000	288,029,000	300,645,000	275,247,000
Basic earnings per share	$ 0.44	$ 0.07	$ 0.86	$ 0.25
Diluted earnings per share	$ 0.44	$ 0.07	$ 0.86	$ 0.24
Earnings Per Share (Textual) [Abstract]
Securities Excluded From Computation Of Diluted Earnings Per Share	0	0	0	0