Leases - Components of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Finance lease income	$ 2.8
Operating lease income:
Variable lease income	253.9
Operating Lease, Variable Lease Income	17.7
Operating Lease, Lease Income	271.6
Total operating lease income	23.7
Total lease income	$ 274.4	$ 273.2