Earnings Per Share ("EPS") of Common Stock - Reconciliation of Numerator and Denominator (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022
Numerator:
Net income	$ 13.7	$ 42.5	$ 57.9	$ 105.6
Income allocated to participating securities	(0.1)	(0.3)	(0.2)	(0.7)
Net income for basic EPS	13.6	42.2	57.7	104.9
Interest on 2¼% Notes	0.1	0.0	1.4	0.0
Net income for diluted EPS	$ 13.7	$ 42.2	$ 59.1	$ 104.9
Denominator:
Basic weighted average shares (in shares)	80.3	79.9	80.3	79.0
Effect of:
2 1/4% Notes (in shares)	0.9	2.4	4.0	2.5
Diluted weighted average shares (in shares)	81.2	82.3	84.3	81.5
Basic
Basic earnings per share (in dollars per share)	$ 0.17	$ 0.53	$ 0.72	$ 1.33
Diluted
Diluted earnings per share (in dollars per share)	$ 0.17	$ 0.51	$ 0.70	$ 1.29
Convertible Debt | 2 1/4% Notes
Diluted
Debt instrument interest rate stated percentage	2.25%	2.25%	2.25%	2.25%	2.25%