Supplemental Data - Supplemental Cash Flow Data (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Disclosure of Cash Flow Information
Cash paid during the year for interest, net of interest expense capitalized	$ 10.9	$ 11.9	$ 11.3
Cash paid during the year for income taxes, net of refunds	13.3	7.6	7.6
Non-cash investing activities:
Liability for equipment acquired	3.2	3.4	5.4
Net cash provided by (used in) changes in working capital
Accounts receivable	11.6	(0.9)	(10.2)
Inventories	8.2	3.8	(11.7)
Income taxes receivable/payable	(5.4)	(1.8)	4.5
Prepaid and other current assets	2.4	(1.8)	(0.4)
Accounts payable	(14.0)	0.3	10.6
Accrued expenses	(3.4)	(0.6)	(4.2)
Other	0.0	0.0	(0.4)
Total	$ (0.6)	$ (1.0)	$ (11.8)