Earnings per Common Share Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2022	Sep. 30, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Net income, basic and diluted			$ 202.2	$ 192.1	$ 161.2
Weighted Average Number of Shares Outstanding, Basic and Diluted [Abstract]
Weighted average common shares outstanding for basic earnings per share computation			103,274,070	61,650,312	63,611,891
Dilutive effect of stock-based compensation (in shares)			66,929	91,516	117,579
Weighted average common shares outstanding for diluted earnings per common share computation			103,340,999	61,741,828	63,729,470
Earnings Per Share, Basic and Diluted [Abstract]
Basic earnings per common share (in dollars per share)			$ 1.96	$ 3.12	$ 2.53
Diluted earnings per common share (in dollars per share)			$ 1.96	$ 3.11	$ 2.53
Restricted Stock [Member]
Earnings Per Share, Basic and Diluted [Abstract]
Antidilutive securities excluded from computation of earnings per share (in shares)		83,952	52,027		291,540
Performance Shares
Earnings Per Share, Basic and Diluted [Abstract]
Antidilutive securities excluded from computation of earnings per share (in shares)	333,767		470,622		3,094