Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Finance lease cost:
Amortization of finance lease assets	$ 0.4	$ 0.7
Interest on lease liabilities	0.3	0.6
Total finance lease cost	0.7	1.3
Operating lease cost	17.3	34.7
Short-term lease cost	6.4	10.7
Variable lease cost	3.9	9.8
Total lease cost	$ 28.3	$ 56.5