Bradley Agreement - Schedule of Interest and Premium Received and Deficiency Payment (Details) - Bradley International Airport parking facilities operating agreement - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deficiency repayments	$ 3.8	$ 3.9	$ 2.0
Interest	1.0	0.9	0.6
Premium	$ 0.4	$ 0.3	$ 0.2

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Balance Type:	na
Period Type:	duration