Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Unrecognized tax benefits—beginning of year	$ 96.1	$ 88.0	$ 83.5
Gross additions—current year tax positions	2.6	7.2	9.2
Gross additions—prior year tax positions	2.0	3.7	2.9
Gross additions (reductions)—purchase accounting adjustments		12.1
Gross reductions—prior year tax positions	(16.6)	(11.7)	(6.9)
Gross reductions—settlements with taxing authorities	(1.0)	(3.2)	(0.7)
Unrecognized tax benefits—end of year	$ 83.1	$ 96.1	$ 88.0