Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income (loss) attributable to common stockholders	$ 280,470	$ 437,671
Denominator for basic earnings per share - weighted average shares (in shares)	391,474	371,426
Effect of dilutive securities:
Employee stock options (in shares)	1	15
Non-vested restricted shares (in shares)	868	720
Redeemable shares (in shares)	1,096	1,096
Employee stock purchase program (in shares)	13	0
Dilutive potential common shares (in shares)	1,978	1,831
Denominator for diluted earnings per share - adjusted weighted average shares (in shares)	393,452	373,257
Basic earnings per share (in USD per share)	$ 0.72	$ 1.18
Diluted earnings per share (in USD per share)	$ 0.71	$ 1.17