Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Computation of basic and diluted earnings per share
Numerator for basic and diluted earnings per share - net income (loss) attributable to common stockholders	$ 334,910	$ 182,043	$ 679,353	$ 685,413
Denominator for basic earnings per share - weighted average shares	358,932	351,765	356,911	346,425
Effect of dilutive securities:
Employee stock options	128	114	119	155
Non-vested restricted shares	526	607	414	498
Redeemable shares	1,651	621	1,308	207
Convertible senior unsecured notes	0	0	0	262
Dilutive potential common shares	2,305	1,342	1,841	1,122
Denominator for diluted earnings per share - adjusted weighted average shares	361,237	353,107	358,752	347,547
Basic earnings per share	$ 0.93	$ 0.52	$ 1.9	$ 1.98
Diluted earnings per share	$ 0.93	$ 0.52	$ 1.89	$ 1.97