Schedule of Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net change in current assets and liabilities, net of acquisitions:
Receivables	$ (54.6)	$ (75.8)	$ (15.1)
Inventories	(7.7)	(37.5)	(23.4)
Other current assets	10.0	(9.0)	(3.2)
Trade payables	8.8	(5.1)	101.5
Accrued liabilities, including payroll and benefits	(3.5)	12.2	6.0
Income taxes payable (refundable)	7.0	(12.6)	2.7
Current assets and liabilities	$ (40.0)	$ (127.8)	$ 68.5