Basis of Presentation and Significant Accounting Policies - Schedule of Calculation of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Basic:
Net income for the period		$ 162.1	$ 102.8	$ 45.0
Weighted average number of common shares during the period (in shares)		41.2	41.3	41.3
Basic (in usd per share)		$ 3.93	$ 2.49	$ 1.09
Diluted:
Weighted average number of common shares during the period (in shares)		41.2	41.3	41.3
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)		41.6	41.5	41.4
Net income per share - diluted (in usd per share)		$ 3.90	$ 2.48	$ 1.09
Revision of Prior Period, Error Correction, Adjustment
Basic:
Net income for the period	$ (8.1)		$ (4.4)	$ (1.3)
Stock options
Weighted average number of common equivalent shares to reflect the dilutive effect of common stock equivalent securities
Stock options (in shares)		0.1	0.0	0.0
RSUs related to incentive compensation
Weighted average number of common equivalent shares to reflect the dilutive effect of common stock equivalent securities
RSUs related to incentive compensation (in shares)		0.3	0.2	0.1