Leases - Lease Cost (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019	Jun. 30, 2019
Leases and Lease cost
Practical expedients	true
Components of lease cost
Amortization of right-of-use assets		$ 0.1	$ 0.1
Total finance lease cost		0.1	0.1
Operating lease cost		6.1	12.7
Short term lease cost		0.6	1.1
Variable lease cost		1.2	1.7
Sublease income		(0.3)	(0.6)
Total lease cost		$ 7.7	$ 15.0
ASU 2016-02
Leases and Lease cost
Lease assets	$ 75.5
Lease liabilities	$ 77.9