Leases Leases - Financial Statement information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating lease assets	$ 22.0	$ 22.0	$ 0.0
Finance lease assets	1.0	1.0
Total lease assets	24.0	24.0
Operating lease liability, current	8.0	8.0
Finance lease liability, current	1.0	1.0
Operating Lease liability, noncurrent	14.0	14.0	$ 0.0
Finance lease liability, noncurrent	1.0	1.0
Total lease liabilities	24.0	24.0
Operating lease cost	2.0	5.0
Amortization of leased assets	0.0	0.0
Interest expense, net of capitalized interest	0.0	0.0
Total lease costs	$ 3.0	$ 5.0