Leases Leases - Lease cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Lease, Cost [Abstract]
Operating lease cost	$ 24.8
Short-term lease cost	3.5
Amortization of right-of-use assets	7.7
Interest on lease liabilities	1.7
Total lease cost	$ 37.7	$ 36.6