Leases - Balance sheet by asset category (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating lease ROU Asset	$ 52.6	$ 39.1
Property, plant and equipment, gross	608.6	557.9
Less: Accumulated depreciation	(396.3)	(357.9)
Property, plant and equipment, net	212.3	200.0	$ 201.9
Finance Leased Asset
Lessee, Lease, Description [Line Items]
Less: Accumulated depreciation	(10.8)	(8.5)
Property, plant and equipment, net	12.9	10.7
Finance Leased Real Estate
Lessee, Lease, Description [Line Items]
Property, plant and equipment, gross	15.8	14.4
Finance Leased Automobile
Lessee, Lease, Description [Line Items]
Property, plant and equipment, gross	0.1
Finance Leased Machinery and Equipment
Lessee, Lease, Description [Line Items]
Property, plant and equipment, gross	7.8	4.8
Real Estate
Lessee, Lease, Description [Line Items]
Operating lease ROU Asset	48.1	33.1
Automobile
Lessee, Lease, Description [Line Items]
Operating lease ROU Asset	3.2	3.0
Machinery and equipment
Lessee, Lease, Description [Line Items]
Operating lease ROU Asset	$ 1.3	$ 3.0