Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Finance lease cost:
Amortization of right-of-use assets	$ 0.2	$ 0.6
Interest on lease liabilities	0.1	0.3
Operating lease cost:
Fixed lease cost - operating leases	15.0	45.4
Total lease cost	15.3	46.3
Sublease Income	$ 17.2	$ 53.0