Financial Instruments and Fair Value Measurements (Narrative) (Details) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2025 USD ($)	Jun. 30, 2025 USD ($) store	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Apr. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment	$ 0.0		$ 0.0	$ 65.3	$ 0.0
Franchise rights impairment, number of stores | store		9
Franchise rights impairment	0.0		0.0	71.7	0.0
Reporting Unit, Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment				65.3
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment				65.3	0.0
Fair Value, Nonrecurring [Member] | Reporting Unit, Mobile Service
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment		$ 65.3
Franchise Rights | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Franchise rights impairment		$ 71.7		71.7	0.0
Franchise Rights | Fair Value, Nonrecurring [Member] | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise rights	42.7		$ 0.0	42.7	$ 0.0
Franchise Rights | Fair Value, Nonrecurring [Member] | Level 3 | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise rights						$ 42.7
Franchise Rights | Fair Value, Nonrecurring [Member] | Level 3 | Measurement Input, Long-Term Revenue Growth Rate [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.020
Franchise Rights | Fair Value, Nonrecurring [Member] | Arithmetic Average [Member] | Level 3 | Measurement Input, Weighted Average Cost of Capital [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.090
Franchise Rights | Fair Value, Nonrecurring [Member] | Arithmetic Average [Member] | Level 3 | Measurement Input, Discount Rate [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.104
Franchise Rights | Fair Value, Nonrecurring [Member] | Arithmetic Average [Member] | Level 3 | Measurement Input, Long-term Pretax Loss Margin [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.024
Franchise Rights | Fair Value, Nonrecurring [Member] | Arithmetic Average [Member] | Level 3 | Measurement Input, Contributory Asset Charges [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.062
Franchise Rights | Fair Value, Nonrecurring [Member] | Minimum | Level 3 | Measurement Input, Weighted Average Cost of Capital [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.089
Franchise Rights | Fair Value, Nonrecurring [Member] | Minimum | Level 3 | Measurement Input, Discount Rate [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.096
Franchise Rights | Fair Value, Nonrecurring [Member] | Minimum | Level 3 | Measurement Input, Long-term Pretax Loss Margin [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.000
Franchise Rights | Fair Value, Nonrecurring [Member] | Minimum | Level 3 | Measurement Input, Contributory Asset Charges [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.051
Franchise Rights | Fair Value, Nonrecurring [Member] | Maximum | Level 3 | Measurement Input, Weighted Average Cost of Capital [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.091
Franchise Rights | Fair Value, Nonrecurring [Member] | Maximum | Level 3 | Measurement Input, Discount Rate [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.113
Franchise Rights | Fair Value, Nonrecurring [Member] | Maximum | Level 3 | Measurement Input, Long-term Pretax Loss Margin [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.059
Franchise Rights | Fair Value, Nonrecurring [Member] | Maximum | Level 3 | Measurement Input, Contributory Asset Charges [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Franchise Rights, Measurement Input						0.084
Carrying value | Continuing Operations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for sale	$ 63.2			$ 63.2			$ 23.6