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, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Calculation of basic earnings (loss) per share:
Net income (loss) applicable to common stock	$ 197.7	$ (213.9)	$ 288.2	$ (822.5)
Weighted-average common shares outstanding - basic (in shares)	156.0	126.8	155.8	121.3
Basic earnings (loss) per share (in dollars per share)	$ 1.27	$ (1.69)	$ 1.85	$ (6.78)
Calculation of diluted earnings (loss) per share:
Net income (loss) applicable to common stock	$ 197.7	$ (213.9)	$ 288.2	$ (822.5)
Convertible Notes	4.3	0.0	8.6	0.0
Diluted income (loss) applicable to common stock	$ 202.0	$ (213.9)	$ 296.8	$ (822.5)
Weighted average common shares outstanding - diluted (in shares)	172.7	126.8	172.8	121.3
Diluted earnings (loss) per share (in dollars per share)	$ 1.17	$ (1.69)	$ 1.72	$ (6.78)
Effective tax rate	21.10%	21.40%	20.30%	16.10%
Convertible Notes
Calculation of diluted earnings (loss) per share:
Effective tax rate	20.00%		20.00%