Significant Accounting Policies - Basic and Diluted Earnings from Continuing Operations Per Common Share (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Basic weighted-average common shares outstanding	61.8	62.3	61.9	62.4
Effect of dilutive employee and director awards	0.2	0.2	0.2	0.1
Diluted weighted-average common shares outstanding	62.0	62.5	62.1	62.5