Earnings 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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Calculation of basic earnings per share:
Net income applicable to common stock	$ 26.0	$ 197.7	$ 77.5	$ 288.2
Weighted-average common shares outstanding - basic (in shares)	164.8	156.0	166.5	155.8
Basic earnings per share (in dollars per share)	$ 0.16	$ 1.27	$ 0.47	$ 1.85
Calculation of diluted earnings per share:
Net income applicable to common stock	$ 26.0	$ 197.7	$ 77.5	$ 288.2
Convertible Notes	1.8	4.3	3.7	8.6
Diluted income applicable to common stock	$ 27.8	$ 202.0	$ 81.2	$ 296.8
Weighted average common shares outstanding - diluted (in shares)	180.2	172.7	182.3	172.8
Diluted earnings per share (in dollars per share)	$ 0.15	$ 1.17	$ 0.45	$ 1.72
Effective tax rate	68.30%	21.10%	57.20%	20.30%
Convertible Notes
Calculation of diluted earnings per share:
Effective tax rate	21.00%	20.00%	21.00%	20.00%
Common Stock, Non-Exchangeable
Calculation of basic earnings per share:
Weighted-average common shares outstanding - basic (in shares)	164.2	156.0	165.9	155.8
Common Stock, Exchangeable
Calculation of basic earnings per share:
Weighted-average common shares outstanding - basic (in shares)	0.6	0.0	0.6	0.0