Leases - Components of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating lease income:
Variable lease income	$ 268.3	$ 252.0	$ 530.4	$ 506.1
Operating Lease, Variable Lease Income	17.7	15.7	34.5	30.5
Operating Lease, Lease Income	286.0	267.7	564.9	536.6
Finance lease income	1.6	1.6	3.3	3.4
Total lease income	287.6	269.3	568.2	540.0
Total operating lease income	$ 18.9	$ 23.7	$ 35.7	$ 46.4