Leases - Cash flows (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Leases
Operating cash flows from operating leases	$ 5.9
Operating cash flows from finance leases	0.1
Financing cash flows from finance leases	0.8
Total cash paid for amounts included in the measurement of lease liabilities	6.8
Finance lease liabilities arising from obtaining right-of-use assets	0.3
Operating lease liabilities arising from obtaining right-of-use assets	$ 0.3