Bradley Agreement - Schedule of Interest and Premium Received and Deficiency Payments (Details) - Bradley International Airport Parking Facilities Operating Agreement - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Loss Contingencies [Line Items]
Deficiency repayments	$ 0.0	$ 1.8	$ 0.1	$ 2.4
Interest	0.0	0.5	0.1	0.5
Premium	$ 0.0	$ 0.2	$ 0.0	$ 0.2