v3.10.0.1

Investments (Narrative) (Details) € in Millions			3 Months Ended			6 Months Ended
	Jan. 04, 2017 EUR (€)	Jan. 04, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 EUR (€)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 EUR (€)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016
Schedule of Investments [Line Items]
Dividends from affiliates and others						$ 130,100,000	$ 104,800,000
Value-added taxes (VAT) paid on behalf of the VodafoneZiggo JV						0	162,600,000
Distributions received from affiliates						0	1,569,400,000
VodafoneZiggo JV
Schedule of Investments [Line Items]
Percent of interest income earned on loan included in investment								100.00%	100.00%
Percent of share-based compensation included in investment								100.00%	100.00%
Percent of remaining results of operations included in investment								50.00%	50.00%
Ownership percentage								50.00%	50.00%	50.00%	50.00%
Co-venturer ownership percentage											50.00%
Dividends from affiliates and others	€ 2,200.0	$ 2,400,000,000		€ 3.9	$ 4,500,000
Value-added taxes (VAT) paid on behalf of the VodafoneZiggo JV					162,600,000
Distributions received from affiliates						116,600,000	87,300,000
Revenue			$ 1,114,500,000		1,081,300,000	2,296,100,000	2,165,200,000
JV Services
Schedule of Investments [Line Items]
Revenue			$ 53,800,000		$ 31,800,000	$ 88,300,000	63,300,000
VodafoneZiggo JV Loan | VodafoneZiggo JV
Schedule of Investments [Line Items]
Due from related party									$ 1,050,900,000	$ 1,081,900,000
Receivable interest rate						5.55%
Receivable annually								€ 100.0	116,800,000
Accrued interests settled in cash						$ 30,200,000
Vodafone
Schedule of Investments [Line Items]
Proceeds from financing arrangements	2,800.0	2,900,000,000
Proceeds from equalization payment from affiliate	€ 802.9	$ 840,800,000
Equity Method Investee | VodafoneZiggo JV
Schedule of Investments [Line Items]
Transfer of assets						$ 30,300,000	$ 107,800,000
Due from related party									$ 46,800,000	$ 33,300,000

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