Earnings (Loss) Per Common Share - Computation of Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								7 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, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Net income (loss)	$ (13,791)	$ (13,129)	$ (19,698)	$ (23,149)	$ (25,193)	$ (15,775)	$ (11,999)	$ (173,811)	$ 347,979	$ (69,767)	$ (226,778)	$ 319,814
Less:
Net income (loss) attributable to non-controlling interests	$ (631)	$ (541)	$ (2,793)	$ (5,137)	$ (7,786)	$ (4,567)	$ (3,612)	$ (51,071)		(9,102)	(67,036)	(12,680)
Undeclared cumulative preferred dividends										0	0	2,184
Net income (loss) available for common shareholders - Basic										(60,665)	(159,742)	330,310
Add:
Net income (loss) attributable to non-controlling interests										0	0	(12,680)
Undeclared cumulative preferred dividends converted during the period										0	0	2,184
Net income (loss) available for common shareholders - Diluted										$ (60,665)	$ (159,742)	$ 319,814
Weighted-average common shares outstanding - Basic (in shares)										64,351,000	45,031,000	25,129,000
Assumed conversion of convertible preferred stock at beginning-of-period (in shares)										0	0	9,397,000
Assumed conversion of Class B common shares to Class A common shares (in shares)										0	0	10,083,000
Weighted-average common shares outstanding - Diluted (in shares)										64,351,000	45,031,000	46,136,000
Earnings (Loss) per Common Share
Basic (in dollars per share)	$ (0.18)	$ (0.18)	$ (0.28)	$ (0.34)	$ (0.33)	$ (0.26)	$ (0.20)	$ (2.91)		$ (0.94)	$ (3.55)	$ 13.14
Diluted (in dollars per share)	$ (0.18)	$ (0.18)	$ (0.28)	$ (0.34)	$ (0.33)	$ (0.26)	$ (0.20)	$ (2.91)		$ (0.94)	$ (3.55)	$ 6.93
Class A
Earnings (Loss) per Common Share
Convertible preferred stock, shares issued upon conversion	1									1
Restricted stock and RSUs
Add:
Dilutive effect of share-based payment arrangements (in shares)										0	0	17,000
Stock options
Add:
Dilutive effect of share-based payment arrangements (in shares)										0	0	1,510,000