Intangible Assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions		Sep. 30, 2025	Dec. 31, 2024
Finite-Lived Intangible Assets [Line Items]
Gross		$ 2,459.0	$ 2,444.2
Accumulated amortization		(1,351.0)	(1,306.4)
Impairment		(485.8)	(485.8)
Intangible assets		622.2	652.0
Permits and leasehold agreements
Finite-Lived Intangible Assets [Line Items]
Gross		1,536.7	1,535.9
Accumulated amortization		(971.1)	(935.7)
Intangible assets		565.6	600.2
Franchise agreements
Finite-Lived Intangible Assets [Line Items]
Gross		904.2	888.8
Accumulated amortization		(368.8)	(360.9)
Impairment		(485.8)	(485.8)
Intangible assets	[1]	49.6	42.1
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross		18.1	19.5
Accumulated amortization		(11.1)	(9.8)
Intangible assets		$ 7.0	$ 9.7

[1] We reclassified all Prepaid MTA equipment deployment costs (see Note 17. Commitments and Contingencies) and recorded impairments in the first and second quarters of 2024, due to the long-term outlook of our Transit reporting unit.