SEGMENT INFORMATION - Summary of Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue from External Customer [Line Items]
Revenues	$ 2,417,801	$ 2,322,521	$ 7,111,668	$ 6,947,142
Pay TV
Revenue from External Customer [Line Items]
Revenues	1,054,667	1,069,946	3,122,779	3,224,987
Broadband
Revenue from External Customer [Line Items]
Revenues	729,907	658,278	2,143,730	1,926,816
Telephony
Revenue from External Customer [Line Items]
Revenues	161,351	172,479	490,888	531,701
Business services and wholesale
Revenue from External Customer [Line Items]
Revenues	344,193	324,642	1,014,671	967,703
Advertising
Revenue from External Customer [Line Items]
Revenues	123,066	89,292	320,546	270,154
Other
Revenue from External Customer [Line Items]
Revenues	4,617	7,884	19,054	25,781
Operating Segments | Cablevision
Revenue from External Customer [Line Items]
Revenues	1,721,688	1,661,359	5,058,709	4,962,872
Operating Segments | Cablevision | Pay TV
Revenue from External Customer [Line Items]
Revenues	783,252	798,583	2,313,229	2,397,233
Operating Segments | Cablevision | Broadband
Revenue from External Customer [Line Items]
Revenues	457,709	416,972	1,347,486	1,218,504
Operating Segments | Cablevision | Telephony
Revenue from External Customer [Line Items]
Revenues	130,494	140,830	399,714	432,710
Operating Segments | Cablevision | Business services and wholesale
Revenue from External Customer [Line Items]
Revenues	242,305	230,200	713,240	689,708
Operating Segments | Cablevision | Advertising
Revenue from External Customer [Line Items]
Revenues	105,719	72,316	276,343	216,250
Operating Segments | Cablevision | Other
Revenue from External Customer [Line Items]
Revenues	2,209	2,458	8,697	8,467
Operating Segments | Cequel Corp. [Member]
Revenue from External Customer [Line Items]
Revenues	696,873	661,642	2,062,297	1,984,750
Operating Segments | Cequel Corp. [Member] | Pay TV
Revenue from External Customer [Line Items]
Revenues	271,415	271,363	809,550	827,754
Operating Segments | Cequel Corp. [Member] | Broadband
Revenue from External Customer [Line Items]
Revenues	272,198	241,306	796,244	708,312
Operating Segments | Cequel Corp. [Member] | Telephony
Revenue from External Customer [Line Items]
Revenues	30,857	31,649	91,174	98,991
Operating Segments | Cequel Corp. [Member] | Business services and wholesale
Revenue from External Customer [Line Items]
Revenues	101,888	94,442	301,431	277,995
Operating Segments | Cequel Corp. [Member] | Advertising
Revenue from External Customer [Line Items]
Revenues	18,107	17,456	53,541	54,384
Operating Segments | Cequel Corp. [Member] | Other
Revenue from External Customer [Line Items]
Revenues	2,408	5,426	10,357	17,314
Eliminations
Revenue from External Customer [Line Items]
Revenues	(760)	(480)	(9,338)	(480)
Eliminations | Pay TV
Revenue from External Customer [Line Items]
Revenues	0	0	0	0
Eliminations | Broadband
Revenue from External Customer [Line Items]
Revenues	0	0	0	0
Eliminations | Telephony
Revenue from External Customer [Line Items]
Revenues	0	0	0	0
Eliminations | Business services and wholesale
Revenue from External Customer [Line Items]
Revenues	0	0	0	0
Eliminations | Advertising
Revenue from External Customer [Line Items]
Revenues	(760)	(480)	(9,338)	(480)
Eliminations | Other
Revenue from External Customer [Line Items]
Revenues	$ 0	$ 0	$ 0	$ 0