Investments (Schedule of Investments) (Details) £ in Millions, $ in Millions			3 Months Ended
	Feb. 16, 2024 USD ($)	Feb. 16, 2024 GBP (£)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Schedule of Investments [Line Items]
Equity			$ 9,890.4	$ 9,987.6
Short-term, separately-managed accounts (SMAs)			1,652.8	1,990.5
Total investments			5,224.7	5,399.0
Total investments			15,115.1	15,386.6
Short-term investments			1,652.8	1,990.5
Long-term investments			$ 13,462.3	$ 13,396.1
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]			Other current assets (notes 3 and 4)	Other current assets (notes 3 and 4)
Accrued interest			$ 35.2	$ 34.6
VMO2 JV
Schedule of Investments [Line Items]
Equity			$ 7,175.1	7,248.5
Ownership percentage			50.00%
VodafoneZiggo JV
Schedule of Investments [Line Items]
Equity			$ 1,998.5	2,055.4
Ownership percentage			50.00%
VodafoneZiggo JV | VodafoneZiggo JV Loan
Schedule of Investments [Line Items]
Excess of carrying amount over proportional share in investees net assets			$ 1,213.8	1,234.7
Related party note receivable rate			5.55%
Interest accrued			$ 13.8
VodafoneZiggo JV | VodafoneZiggo JV Receivable I
Schedule of Investments [Line Items]
Related party note receivable			755.8	774.5
VodafoneZiggo JV | VodafoneZiggo JV Receivable II
Schedule of Investments [Line Items]
Related party note receivable			224.4	230.0
AtlasEdge JV
Schedule of Investments [Line Items]
Equity			$ 272.0	250.8
Ownership percentage			48.20%
All3Media Ltd. (All3Media) (d)
Schedule of Investments [Line Items]
Equity			$ 149.4	144.2
Ownership percentage	100.00%	100.00%	50.00%
Cash proceeds from equity sale	$ 397.7	£ 315.0
Formula E Holdings Ltd (Formula E)
Schedule of Investments [Line Items]
Equity			$ 101.9	99.1
Ownership percentage			35.90%
nexfibre JV
Schedule of Investments [Line Items]
Equity			$ 67.8	55.9
Ownership percentage			25.00%
Other
Schedule of Investments [Line Items]
Equity			$ 125.7	133.7
Long-term investments at fair value			369.6	361.9
Vodafone - subject to re-use rights
Schedule of Investments [Line Items]
Long-term, SMAs			1,187.6	1,168.1
Total investments			$ 122.3	115.5
Ownership percentage			4.90%
EdgeConneX, Inc. (EdgeConneX)
Schedule of Investments [Line Items]
Long-term investments at fair value			$ 402.8	318.3
Ownership percentage			5.20%
Televisa Univision, Inc. (Televisa Univision)
Schedule of Investments [Line Items]
Long-term, SMAs			$ 388.3	388.3
Ownership percentage			6.00%
SMAs
Schedule of Investments [Line Items]
Long-term, SMAs			$ 376.7	285.6
ITV plc (ITV)
Schedule of Investments [Line Items]
Long-term investments at fair value			$ 371.9	321.9
Ownership percentage			9.90%
Plume Design, Inc. (Plume)
Schedule of Investments [Line Items]
Long-term, SMAs			$ 167.3	168.4
Ownership percentage			11.50%
Warrants, fair value			$ 60.9	61.3
Pax8, Inc.
Schedule of Investments [Line Items]
Long-term, SMAs			$ 101.1	100.3
Ownership percentage			5.60%
CANAL+ Polska S.A.
Schedule of Investments [Line Items]
Long-term investments at fair value			$ 75.2	76.4
Ownership percentage			17.00%
Lions Gate Entertainment Corp. (Lionsgate)
Schedule of Investments [Line Items]
Long-term investments at fair value			$ 63.6	69.6
Ownership percentage			2.80%
Aviatrix Systems, Inc. (Aviatrix)
Schedule of Investments [Line Items]
Long-term investments at fair value			$ 41.2	55.5
Ownership percentage			3.30%
Lacework, Inc. (Lacework)
Schedule of Investments [Line Items]
Long-term investments at fair value			$ 26.6	$ 94.2
Ownership percentage			3.30%