Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Basic earnings per share:
Net income	$ 25.6	$ 25.6
Weighted average number of shares outstanding	32.0	32.0
Basic earnings per share from net income	$ 0.80	$ 0.80
Diluted earnings per share:
Net income	$ 25.6	$ 25.6
Weighted average number of shares outstanding	32.0	32.0
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Restricted stock	0.1	0.1
Total shares and dilutive securities	32.1	32.1
Net income	$ 0.80	$ 0.80