Supplemental Cash Flow Information - Schedule Of Noncash Investing and Financing Activities (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Accrued liabilities for purchases of property, plant and equipment	$ 61.5	$ 54.2	$ 67.0
Remeasurement of operating lease right-of-use assets	2.2	2.0
Right-of-use assets obtained in exchange for new operating lease liabilities	31.9	45.7
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 19.4	0.2
Acquisition of assets through asset exchange		$ 2.4
Acquisition of assets through capital lease			$ 1.1