Earnings (Loss) per Share - Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Calculation of basic earnings (loss) per share:
Net income (loss) applicable to common stock	$ (213.9)	$ 51.6	$ (822.5)	$ 92.5
Weighted average common shares outstanding - basic (in shares)	126.8	116.0	121.3	116.1
Basic earnings (loss) per share (in dollars per share)	$ (1.69)	$ 0.44	$ (6.78)	$ 0.80
Calculation of diluted earnings (loss) per share:
Net income (loss) applicable to common stock	$ (213.9)	$ 51.6	$ (822.5)	$ 92.5
Weighted average common shares outstanding - diluted (in shares)	126.8	117.7	121.3	118.2
Diluted earnings (loss) per share (in dollars per share)	$ (1.69)	$ 0.44	$ (6.78)	$ 0.78