Earnings Per Share - Summary of Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income (loss) attributable to common stockholders	$ (6,793)	$ (10,214)	$ 103,016	$ 372	$ (6,489)	$ (139)	$ 3,188	$ (6,494)	$ 86,381	$ (9,934)	$ (4,419)
Earnings allocated to unvested participating securities									(98)	(37)
Numerator for income (loss) per common share - basic and diluted									$ 86,283	$ (9,971)	$ (4,419)
Denominator:
Denominator for basic income (loss) per common share - weighted average shares									236,372,801	218,053,062	212,106,718
Effect of dilutive employee stock options and restricted share awards									29,000
Denominator for diluted income (loss) per common share - weighted average shares									236,401,548	218,053,062	212,106,718
Income (loss) per common share - basic and diluted									$ 0.37	$ (0.05)	$ (0.02)