Derivative Instruments (Fair Values of Derivative Assets and Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2017	May 22, 2017	Dec. 31, 2016
Assets:
Current	$ 345.1		$ 412.7
Long-term	2,236.0		2,763.4
Total	2,581.1		3,176.1
Liabilities:
Current	319.3		281.2
Long-term	1,122.9		1,028.7
Total	1,442.2		1,309.9
Cross-Currency and Interest Rate Derivative Contracts [Member]
Assets:
Current	326.3		344.4
Long-term	1,673.2		2,262.1
Total	1,999.5		2,606.5
Liabilities:
Current	291.8		263.7
Long-term	1,122.4		1,028.5
Total	1,414.2		1,292.2
Equity-Related Derivative Instruments [Member]
Assets:
Total	556.6	$ 51.0	524.0
Liabilities:
Total	8.8		8.6
Foreign Exchange Contract [Member]
Assets:
Current	18.4		31.0
Long-term	5.7		14.1
Total	24.1		45.1
Liabilities:
Current	18.7		8.9
Long-term	0.5		0.1
Total	19.2		9.0
Other Contract [Member]
Assets:
Total	0.9		0.5
Liabilities:
Total			0.1
Liberty Global Group [Member]
Assets:
Current	336.0		405.5
Long-term	2,128.2		2,624.4
Total	2,464.2		3,029.9
Liabilities:
Current	289.1		252.4
Long-term	1,108.3		999.8
Total	1,397.4		1,252.2
Liberty Global Group [Member] | Cross-Currency and Interest Rate Derivative Contracts [Member]
Assets:
Current	320.0		337.5
Long-term	1,566.2		2,123.1
Total	1,886.2		2,460.6
Liabilities:
Current	264.0		239.1
Long-term	1,107.8		999.6
Total	1,371.8		1,238.7
Liberty Global Group [Member] | Equity-Related Derivative Instruments [Member]
Assets:
Current	0.0		37.1
Long-term	556.6		486.9
Total	556.6		524.0
Liabilities:
Current	8.8		8.6
Long-term	0.0		0.0
Total	8.8		8.6
Liberty Global Group [Member] | Foreign Exchange Contract [Member]
Assets:
Current	15.6		30.7
Long-term	4.9		14.1
Total	20.5		44.8
Liabilities:
Current	16.3		4.7
Long-term	0.5		0.1
Total	16.8		4.8
Liberty Global Group [Member] | Other Contract [Member]
Assets:
Current	0.4		0.2
Long-term	0.5		0.3
Total	0.9		0.5
Liabilities:
Current	0.0		0.0
Long-term	0.0		0.1
Total	0.0		0.1
LiLAC Group [Member]
Assets:
Current	9.1		7.2
Long-term	107.8		139.0
Total	116.9		146.2
Liabilities:
Current	30.2		28.8
Long-term	14.6		28.9
Total	44.8		57.7
LiLAC Group [Member] | Cross-Currency and Interest Rate Derivative Contracts [Member]
Assets:
Current	6.3		6.9
Long-term	107.0		139.0
Total	113.3		145.9
Liabilities:
Current	27.8		24.6
Long-term	14.6		28.9
Total	42.4		53.5
LiLAC Group [Member] | Foreign Exchange Contract [Member]
Assets:
Current	2.8		0.3
Long-term	0.8		0.0
Total	3.6		0.3
Liabilities:
Current	2.4		4.2
Long-term	0.0		0.0
Total	$ 2.4		$ 4.2