Income Taxes - Reconciliations of Statutory U.S. Federal Income Tax Rates to Our Effective Tax Rate for Continuing Operations (Parenthetical) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)
Income Tax Disclosure [Abstract]
Regulatory expenses related to resolution of state attorneys general litigation and investigations	$ 205.0
Regulatory expenses non deductible for income tax purposes	$ 50.7