Intangible Assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions		Mar. 31, 2026	Dec. 31, 2025
Intangible Asset, Finite-Lived [Line Items]
Gross		$ 2,429.8	$ 2,465.3
Accumulated amortization		(1,340.4)	(1,367.5)
Impairment		(485.8)	(485.8)
Intangible assets		603.6	612.0
Permits and leasehold agreements
Intangible Asset, Finite-Lived [Line Items]
Gross		1,545.1	1,538.1
Accumulated amortization		(996.7)	(983.8)
Intangible assets		548.4	554.3
Franchise agreements
Intangible Asset, Finite-Lived [Line Items]
Gross		866.6	909.0
Accumulated amortization		(330.8)	(371.7)
Impairment		(485.8)	(485.8)
Intangible assets	[1]	50.0	51.5
Other intangible assets
Intangible Asset, Finite-Lived [Line Items]
Gross		18.1	18.2
Accumulated amortization		(12.9)	(12.0)
Intangible assets		$ 5.2	$ 6.2

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