Maturities of lease liabilities (Details) $ in Millions	Mar. 31, 2019 USD ($)
Leases [Abstract]
2019 (excluding the three months ended March 31, 2019)	$ 67.2
2020	58.1
2021	36.8
2022	23.0
2023	14.7
Thereafter	25.3
Total	225.1
Less: Present value discount	(53.0)
Lease liability	172.1
2019 (excluding the three months ended March 31, 2019)	0.8
2020	1.0
2021	1.0
2022	0.0
2023	0.0
Thereafter	0.0
Total	2.8
Less: Present value discount	(0.7)
Lease liability	$ 2.1