Commitment and Contingencies - Narrative (Details) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) Displays	Sep. 30, 2019 USD ($) Displays	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Other Commitments [Line Items]
MTA equipment development cost additions \| $		$ 101.1		$ 91.2
Subsequent Event
Other Commitments [Line Items]
MTA equipment development cost additions \| $			$ 150.0
Standalone letters of credit and sublimit to revolving credit facility [Member]
Other Commitments [Line Items]
Letters of credit outstanding, amount \| $	$ 73.0	73.0
Surety Bond
Other Commitments [Line Items]
Surety bonds outstanding \| $	$ 162.1	$ 162.1
MTA digital advertising screens on subway and train platforms
Other Commitments [Line Items]
Number of displays	8,565	8,565
MTA smaller-format digital advertising screens rolling stock
Other Commitments [Line Items]
Number of displays	37,716	37,716
MTA communication displays
Other Commitments [Line Items]
Number of displays	7,829	7,829
MTA displays installed
Other Commitments [Line Items]
Number of displays	3,740	3,740
Number of display additions	972	2,511