Earnings (Loss) per Share - Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Calculation of basic earnings (loss) per share:
Net income (loss) applicable to common stock	$ 85.7	$ 141.1	$ 373.9	$ (680.6)
Weighted-average common shares outstanding - basic (in shares)	156.1	138.2	155.9	126.9
Basic earnings (loss) per share (in dollars per share)	$ 0.55	$ 1.02	$ 2.40	$ (5.36)
Calculation of diluted earnings (loss) per share:
Net income (loss) applicable to common stock	$ 85.7	$ 141.1	$ 373.9	$ (680.6)
Convertible Notes	4.4	4.2	13.0	0.0
Diluted income (loss) applicable to common stock	$ 90.1	$ 145.3	$ 386.9	$ (680.6)
Weighted average common shares outstanding - diluted (in shares)	172.7	155.5	172.7	126.9
Diluted earnings (loss) per share (in dollars per share)	$ 0.52	$ 0.93	$ 2.24	$ (5.36)
Effective tax rate	29.70%	(11.30%)	22.70%	20.20%
Convertible Notes
Calculation of diluted earnings (loss) per share:
Effective tax rate	20.00%		20.00%