Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income (loss)	$ 74.9	$ (15.8)	$ 26.2	$ (268.9)	$ (33.9)	$ (13.7)	$ (18.9)	$ (74.3)	$ (183.6)	$ (140.8)	$ (314.0)
Weighted-average number of ordinary shares outstanding - basic (in shares)	330,335,268	328,411,705	328,411,705	240,656,864					307,076,397	118,261,955	118,261,955
Dilutive effect of equity-based compensation and warrants (in shares)									0	0	0
Weighted-average number of ordinary shares outstanding - diluted (in shares)	345,136,798	328,411,705	331,136,080	240,656,864					307,076,397	118,261,955	118,261,955
Net income per share
Basic (USD per share)	$ 0.23	$ (0.05)	$ 0.08	$ (1.12)					$ (0.60)	$ (1.19)	$ (2.65)
Diluted (USD per share)	$ 0.22	$ (0.05)	$ 0.08	$ (1.12)					$ (0.60)	$ (1.19)	$ (2.65)
Share Capital
Net income per share
Common stock shares exchange ratio (in shares)											118.261955	118,261,955
Previously Reported | Share Capital
Net income per share
Common stock shares exchange ratio (in shares)											1.0	1,000,000.0