Loss Per Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basic and diluted:
Net loss attributable to common shareholders	$ (114,000,000)	$ (68,000,000)	$ (63,000,000)	$ (32)	$ (136,000,000)	$ (33,000,000)	$ (28,000,000)	$ (20,000,000)	$ (276,000,000)	$ (217,000,000)	$ (53,000,000)
Basic: Weighted average number of shares outstanding (in millions) (in shares)									87,160,000	87,130,000	87,130,000
Diluted: Weighted-average number of shares outstanding, assuming dilution (in millions) (in shares)									87,160,000	87,130,000	87,130,000
Basic loss per share (in dollars per share)	$ (1.31)	$ (0.78)	$ (0.72)	$ (0.36)	$ (1.56)	$ (0.38)	$ (0.32)	$ 0	$ (3.17)	$ (2.49)	$ (0.61)
Diluted loss per share (in dollars per share)	$ (1.31)	$ (0.78)	$ (0.72)	$ (0.36)	$ (1.56)	$ (0.38)	$ (0.32)	$ 0	$ (3.17)	$ (2.49)	$ (0.61)
Anti-dilutive shares excluded from loss per shares (in shares)									446,821	0	0