Leases - Schedule of Lease Assets and Liabilities Included on Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Operating Leases:
Operating lease right-of-use assets	$ 34.1	$ 33.9	$ 38.6
Current maturities of operating lease right-of-use assets	9.1	9.1	9.8
Operating lease right-of-use liabilities, less current maturities	25.0	24.9	29.0
Total operating lease liabilities	34.1	34.0	38.8
Finance Leases:
Gross property, plant and equipment	11.7	11.1	10.8
Accumulated depreciation	(6.8)	(6.3)	(5.7)
Property, plant and equipment, net	$ 4.9	$ 4.8	$ 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	2.1	1.9	2.3
Total finance lease liabilities	$ 3.6	$ 3.3	$ 3.7