Earnings and Dividends per Common Share - Schedule of Computation of Basic and Diluted Earnings per Common Share (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
(Loss) gain on sale of discontinued operations, tax benefit (expense)	$ 0.0	$ 0.1	$ (7.4)