Supplemental Cash Flow Information - Schedule Of Noncash Investing and Financing Activities (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Accrued liabilities for purchases of property, plant and equipment	$ 54.2	$ 67.0	$ 61.6
Acquisition of assets through asset exchange	2.4		2.5
Remeasurement of operating lease right-of-use assets	2.0
Right-of-use assets obtained in exchange for new operating lease liabilities	45.7
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 0.2
Acquisition of assets through capital lease		$ 1.1	0.8
Sale of asset to settle liability			$ 0.9