Debt (UPCB SPE Notes) (Details)	Sep. 30, 2021 USD ($)	Sep. 30, 2021 EUR (€)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Borrowings outstanding	$ 14,650,900,000		$ 14,516,300,000
Total carrying amount of debt	$ 14,590,600,000		14,397,900,000
UPCB Finance VII Euro Notes
Debt Instrument [Line Items]
Interest rate	3.625%	3.625%
Debt Instrument, Face Amount | €		€ 600,000,000.0
Borrowings outstanding	$ 694,200,000	€ 600,000,000.0
Total carrying amount of debt	$ 690,100,000
2031 UPC Senior Secured Notes
Debt Instrument [Line Items]
Interest rate	4.875%	4.875%
Debt Instrument, Face Amount	$ 1,250,000,000
Borrowings outstanding	1,250,000,000
Total carrying amount of debt	1,248,600,000
UPCB SPE Notes
Debt Instrument [Line Items]
Borrowings outstanding	1,944,200,000		$ 1,393,700,000
Total carrying amount of debt	$ 1,938,700,000