Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income (loss) attributable to common stockholders	$ 589,876	$ 64,384	$ 1,008,108	$ 656,487
Denominator for basic earnings per share - weighted average shares (in shares)	405,023,000	373,023,000	400,441,000	372,052,000
Effect of dilutive securities:
Employee stock options (in shares)	0	6,000	0	12,000
Non-vested restricted shares (in shares)	757,000	348,000	860,000	464,000
Redeemable shares (in shares)	1,096,000	1,096,000	1,096,000	1,096,000
Employee stock purchase program (in shares)	15,000	14,000	15,000	14,000
Dilutive potential common shares (in shares)	1,868,000	1,464,000	1,971,000	1,586,000
Denominator for diluted earnings per share - adjusted weighted average shares (in shares)	406,891,000	374,487,000	402,412,000	373,638,000
Basic earnings per share (in USD per share)	$ 1.46	$ 0.17	$ 2.52	$ 1.76
Diluted earnings per share (in USD per share)	$ 1.45	$ 0.17	$ 2.51	$ 1.76
Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of shares not included in the computation of diluted earnings per share because such options were anti-dilutive (in shares)			5,152,658