Leases - Schedule of Lease Assets and Liabilities Included on Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Operating Leases:
Operating lease right-of-use assets	$ 36.3	$ 40.9	$ 39.5
Current maturities of operating lease right-of-use assets	9.6	9.7	9.6
Operating lease right-of-use liabilities, less current maturities	27.0	31.6	30.5
Total operating lease liabilities	36.6	41.3	40.1
Finance Leases:
Gross property, plant and equipment	11.1	10.6	10.0
Accumulated depreciation	(6.0)	(5.2)	(4.9)
Property, plant and equipment, net	$ 5.1	$ 5.4	$ 5.1
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentNet	us-gaap:PropertyPlantAndEquipmentNet	us-gaap:PropertyPlantAndEquipmentNet
Current maturities of long-term lease liabilities	$ 1.5	$ 1.4	$ 1.4
Long-term lease liabilities, less current maturities	2.2	2.8	2.9
Total finance lease liabilities	$ 3.7	$ 4.2	$ 4.3