Provisions for Federal and State Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current Income Tax Provision
Federal		$ 0.3
State	$ 0.7	0.6	$ 0.3
Total Current Income Taxes	0.7	0.9	0.3
Deferred Income Tax Provision
Federal	7.3	6.5	9.4
State	3.5	2.8	4.1
Total Deferred Income Taxes	10.8	9.3	13.5
Total Income Tax Expense	$ 11.5	$ 10.2	$ 13.8