Investments (Schedules) (Details) - USD ($)
$ in Millions |
3 Months Ended |
12 Months Ended |
Dec. 31, 2019 |
Sep. 30, 2019 |
Jun. 30, 2019 |
Mar. 31, 2019 |
Dec. 31, 2018 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Equity |
$ 3,492.8
|
|
|
|
$ 3,947.0
|
|
|
|
$ 3,492.8
|
$ 3,947.0
|
|
| Fair value |
1,289.2
|
|
|
|
1,174.8
|
|
|
|
1,289.2
|
1,174.8
|
|
| Total |
4,782.0
|
|
|
|
5,121.8
|
|
|
|
4,782.0
|
5,121.8
|
|
| Realized and unrealized gains (losses) due to changes in fair values of certain investments, net |
|
|
|
|
|
|
|
|
99.0
|
(393.2)
|
$ 228.1
|
| Share of results of affiliates, net |
|
|
|
|
|
|
|
|
(198.5)
|
(8.7)
|
(95.2)
|
| Summarized Financial Condition |
|
|
|
|
|
|
|
|
|
|
|
| Revenue |
2,982.2
|
$ 2,840.9
|
$ 2,850.4
|
$ 2,868.0
|
2,949.1
|
$ 2,929.7
|
$ 3,015.6
|
$ 3,063.5
|
11,541.5
|
11,957.9
|
11,276.4
|
| VodafoneZiggo JV |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Equity |
3,174.1
|
|
|
|
3,761.5
|
|
|
|
3,174.1
|
3,761.5
|
|
| Share of results of affiliates, net |
|
|
|
|
|
|
|
|
(185.9)
|
11.4
|
(70.1)
|
| Summarized Financial Condition |
|
|
|
|
|
|
|
|
|
|
|
| Revenue |
|
|
|
|
|
|
|
|
4,407.8
|
4,602.2
|
4,512.5
|
| Loss before income taxes |
|
|
|
|
|
|
|
|
(512.5)
|
(467.8)
|
(362.9)
|
| Net loss |
|
|
|
|
|
|
|
|
(470.0)
|
(91.6)
|
(259.3)
|
| Current assets |
918.4
|
|
|
|
1,099.6
|
|
|
|
918.4
|
1,099.6
|
|
| Total assets |
21,508.1
|
|
|
|
22,155.7
|
|
|
|
21,508.1
|
22,155.7
|
|
| Total assets |
22,426.5
|
|
|
|
23,255.3
|
|
|
|
22,426.5
|
23,255.3
|
|
| Current liabilities |
2,726.4
|
|
|
|
2,812.3
|
|
|
|
2,726.4
|
2,812.3
|
|
| Long-term liabilities |
14,920.7
|
|
|
|
14,751.5
|
|
|
|
14,920.7
|
14,751.5
|
|
| Long-term liabilities |
4,779.4
|
|
|
|
5,691.5
|
|
|
|
4,779.4
|
5,691.5
|
|
| Total liabilities and owners’ equity |
22,426.5
|
|
|
|
23,255.3
|
|
|
|
22,426.5
|
23,255.3
|
|
| All3Media Group (All3Media) |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Equity |
172.8
|
|
|
|
72.2
|
|
|
|
172.8
|
72.2
|
|
| Share of results of affiliates, net |
|
|
|
|
|
|
|
|
(8.8)
|
(19.2)
|
(25.5)
|
| Formula E Holdings Ltd (Formula E) |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Equity |
105.2
|
|
|
|
45.4
|
|
|
|
105.2
|
45.4
|
|
| Share of results of affiliates, net |
|
|
|
|
|
|
|
|
1.7
|
(0.2)
|
(1.5)
|
| Other |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Equity |
40.7
|
|
|
|
67.9
|
|
|
|
40.7
|
67.9
|
|
| Fair value |
297.6
|
|
|
|
298.2
|
|
|
|
297.6
|
298.2
|
|
| Realized and unrealized gains (losses) due to changes in fair values of certain investments, net |
|
|
|
|
|
|
|
|
(18.4)
|
(11.5)
|
14.4
|
| Share of results of affiliates, net |
|
|
|
|
|
|
|
|
(5.5)
|
(0.7)
|
1.9
|
| ITV plc (ITV) — subject to re-use rights |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Fair value |
798.1
|
|
|
|
634.2
|
|
|
|
798.1
|
634.2
|
|
| Realized and unrealized gains (losses) due to changes in fair values of certain investments, net |
|
|
|
|
|
|
|
|
163.9
|
(257.8)
|
(123.5)
|
| ITI Neovision S.A. (ITI Neovision) |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Fair value |
122.4
|
|
|
|
125.4
|
|
|
|
122.4
|
125.4
|
|
| Realized and unrealized gains (losses) due to changes in fair values of certain investments, net |
|
|
|
|
|
|
|
|
2.7
|
(24.9)
|
15.8
|
| Lions Gate Entertainment Corp (Lionsgate) |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Fair value |
68.0
|
|
|
|
77.5
|
|
|
|
68.0
|
77.5
|
|
| Realized and unrealized gains (losses) due to changes in fair values of certain investments, net |
|
|
|
|
|
|
|
|
(25.0)
|
(86.4)
|
35.3
|
| Casa Systems, Inc. (Casa) |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Fair value |
$ 3.1
|
|
|
|
$ 39.5
|
|
|
|
3.1
|
39.5
|
|
| Realized and unrealized gains (losses) due to changes in fair values of certain investments, net |
|
|
|
|
|
|
|
|
(24.2)
|
(9.2)
|
47.9
|
| Sumitomo |
|
|
|
|
|
|
|
|
|
|
|
| Investment [Line Items] |
|
|
|
|
|
|
|
|
|
|
|
| Realized and unrealized gains (losses) due to changes in fair values of certain investments, net |
|
|
|
|
|
|
|
|
$ 0.0
|
$ (3.4)
|
$ 238.2
|