Income Taxes - Components of Income Tax Expense From Continuing Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Federal income taxes:
Current	$ 174.9	$ 66.3	$ 91.9
Deferred	18.0	61.4	45.4
Total federal income taxes	192.9	127.7	137.3
State income taxes:
Current	35.1	18.7	21.0
Deferred	5.3	6.5	8.7
Total state income taxes	40.4	25.2	29.7
Foreign income taxes:
Current	1.2	0.0	1.2
Deferred	0.3	0.3	0.0
Total foreign income taxes	1.5	0.3	1.2
Income tax expense	$ 234.8	$ 153.2	$ 168.2