Leases Leases - Financial Statement information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating lease assets	$ 22.5	$ 0.0
Finance lease assets	1.9
Total lease assets	24.0
Operating lease liability, current	8.2
Finance lease liability, current	0.6
Operating Lease liability, noncurrent	14.3	$ 0.0
Finance lease liability, noncurrent	1.0
Total lease liabilities	24.0
Operating lease cost	2.3
Amortization of leased assets	0.1
Interest expense, net of capitalized interest	0.0
Total lease costs	$ 2.0