Basis of Presentation and Significant Accounting Policies - Calculation of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Basic:
Net income	$ (16.7)	$ 20.4	$ (4.2)	$ 20.3	$ 46.9	$ 20.2	$ 54.2	$ 49.1	$ 45.0	$ 19.8	[1],[2]	$ 170.4	[1],[2]
Weighted average number of common shares during the period (in shares)	41.4	41.4	41.8	41.9	42.0	42.0	42.0	41.9	41.3	41.6	[1]	42.0	[1]
Basic (in usd per share)	$ (0.40)	$ 0.49	$ (0.10)	$ 0.48	$ 1.12	$ 0.48	$ 1.29	$ 1.17	$ 1.09	$ 0.48	[1]	$ 4.06	[1]
Diluted:
Weighted average number of common shares during the period (in shares)	41.4	41.4	41.8	41.9	42.0	42.0	42.0	41.9	41.3	41.6	[1]	42.0	[1]
Weighted average number of common equivalent shares to reflect the dilutive effect of common stock equivalent securities
CSUs related to deferred compensation for employees (in shares)									0.0	0.0		0.0
Total common and common equivalent shares adjusted to calculate diluted earnings per share (in shares)	41.4	41.6	41.8	42.1	42.2	42.2	42.2	42.1	41.4	41.8	[1]	42.2	[1]
Net income per share - diluted (in usd per share)	$ (0.40)	$ 0.49	$ (0.10)	$ 0.48	$ 1.11	$ 0.48	$ 1.29	$ 1.16	$ 1.09	$ 0.47	[1]	$ 4.04	[1]
Equity Option
Weighted average number of common equivalent shares to reflect the dilutive effect of common stock equivalent securities
Stock options (in shares)									0.0	0.0		0.0
Restricted stock units
Weighted average number of common equivalent shares to reflect the dilutive effect of common stock equivalent securities
RSUs related to incentive compensation (in shares)									0.1	0.2		0.2

[1] Recast for the adoption of ASU 2018-12. See Note 1 of the Consolidated Financial Statements

[2] Recast for the adoption of ASU 2018-12. See Note 1 of the Consolidated Financial Statements