CHANGE IN ACCOUNTING POLICIES AND ATS ACQUISITION - Income Statement (Details) - USD ($) $ in Thousands	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	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue	$ 2,474,549	$ 2,438,662	$ 2,451,081	$ 2,396,567	$ 2,454,940	$ 2,417,801	$ 2,364,153	$ 2,329,714	$ 9,760,859	$ 9,566,608	$ 9,306,950
Programming and other direct costs									3,300,528	3,173,076	3,035,655
Other operating expenses									2,300,398	2,290,266	2,347,315
Restructuring and other expense									72,978		152,401	$ 38,548
Depreciation and amortization (including impairments)									2,263,144	2,382,339	2,930,571
Operating income	427,275	471,515	482,543	442,478	528,724	505,558	335,059	313,038	1,823,811	1,682,379	841,008
Total other income (expense)									(1,636,682)	(1,700,440)	(2,208,596)
Loss before income taxes									187,129	(18,061)	(1,367,588)
Income tax benefit									(47,190)	38,655	2,862,352
Net income	1,331	77,396	86,410	(25,198)	213,808	33,739	(98,004)	(128,949)	139,939	20,594	1,494,764
CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue	2,474,549	2,438,662	2,451,081	2,396,567	2,454,940	2,417,801	2,364,153	2,329,714	9,760,859	9,566,608	9,306,950
Programming and other direct costs									3,300,528	3,173,076	3,035,655
Other operating expenses									2,300,398	2,290,266	2,347,315
Restructuring and other expense									72,978	38,548	152,283
Depreciation and amortization (including impairments)									2,263,144	2,382,339	2,930,571
Operating income	427,275	471,515	482,543	442,478	528,724	505,558	335,059	313,038	1,823,811	1,682,379	841,126
Total other income (expense)									(1,539,751)	(1,364,490)	(1,091,001)
Loss before income taxes									284,060	317,889	(249,875)
Income tax benefit									(71,243)	(57,563)	2,827,751
Net income	21,022	95,517	104,142	(7,864)	242,020	86,747	21,527	(89,968)	212,817	260,326	2,577,876
Video
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue		993,158	1,018,426	1,017,330	1,033,649	1,054,667	1,034,404	1,033,708	3,997,873	4,156,428	4,274,122
Video | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue	968,959	993,158	1,018,426	1,017,330	1,033,649	1,054,667	1,034,404	1,033,708	3,997,873	4,156,428	4,274,122
Broadband
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue		814,328	806,250	775,573	743,725	729,907	712,202	701,621	3,222,605	2,887,455	2,608,595
Broadband | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue	826,454	814,328	806,250	775,573	743,725	729,907	712,202	701,621	3,222,605	2,887,455	2,608,595
Telephony
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue		148,231	150,232	154,464	162,007	161,351	163,499	166,038	598,694	652,895	700,765
Telephony | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue	145,767	148,231	150,232	154,464	162,007	161,351	163,499	166,038	598,694	652,895	700,765
Business services and wholesale
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue		357,628	357,806	350,689	348,087	344,193	337,388	333,090	1,428,532	1,362,758	1,298,213
Business services and wholesale | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue	362,409	357,628	357,806	350,689	348,087	344,193	337,388	333,090	1,428,532	1,362,758	1,298,213
News and advertising (a) | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											396,187
Other (a)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue		4,076	3,917	3,773	4,200	3,770	5,318	6,520	15,987	19,808	29,068
Other (a) | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue	4,221	4,076	3,917	3,773	4,200	3,770	5,318	6,520	15,987	19,808	29,068
Advertising and News [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue		118,067	114,450	94,738	163,272	123,913	111,342	88,737	475,904	487,264	396,187
Advertising and News [Member] | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue	$ 148,649	$ 118,067	$ 114,450	$ 94,738	$ 163,272	$ 123,913	$ 111,342	$ 88,737	$ 475,904	$ 487,264
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											9,326,570
Programming and other direct costs											3,035,655
Other operating expenses											2,342,655
Restructuring and other expense											152,401
Depreciation and amortization (including impairments)											2,930,475
Operating income											865,384
Total other income (expense)											(2,196,733)
Loss before income taxes											(1,331,349)
Income tax benefit											2,852,967
Net income											1,521,618
Previously Reported [Member] | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											6,664,788
Programming and other direct costs											2,280,062
Other operating expenses											1,675,665
Restructuring and other expense											112,384
Depreciation and amortization (including impairments)											2,251,614
Operating income											345,063
Total other income (expense)											(898,612)
Loss before income taxes											(553,549)
Income tax benefit											2,233,716
Net income											1,680,167
Previously Reported [Member] | Video
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											4,214,745
Previously Reported [Member] | Video | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											3,113,238
Previously Reported [Member] | Broadband
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											2,563,772
Previously Reported [Member] | Broadband | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											1,603,015
Previously Reported [Member] | Telephony
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											823,981
Previously Reported [Member] | Telephony | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											693,478
Previously Reported [Member] | Business services and wholesale
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											1,298,817
Previously Reported [Member] | Business services and wholesale | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											923,161
Previously Reported [Member] | News and advertising (a) | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											325,470
Previously Reported [Member] | Other (a)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											29,068
Previously Reported [Member] | Other (a) | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											6,426
Previously Reported [Member] | Advertising and News [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											396,187
Restatement Adjustment | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											(18,515)
Programming and other direct costs											0
Other operating expenses											(18,515)
Restructuring and other expense											0
Depreciation and amortization (including impairments)											0
Operating income											0
Total other income (expense)											0
Loss before income taxes											0
Income tax benefit											0
Net income											0
Restatement Adjustment | Impact of ASU No. 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Programming and other direct costs											0
Other operating expenses											(11,863)
Restructuring and other expense											0
Depreciation and amortization (including impairments)											0
Operating income											11,863
Total other income (expense)											(11,863)
Loss before income taxes											0
Income tax benefit											0
Net income											0
Restatement Adjustment | Video | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											59,878
Restatement Adjustment | Video | Impact of ASU No. 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | Broadband | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											45,192
Restatement Adjustment | Broadband | Impact of ASU No. 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | Telephony | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											(122,981)
Restatement Adjustment | Telephony | Impact of ASU No. 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | Business services and wholesale | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											(604)
Restatement Adjustment | Business services and wholesale | Impact of ASU No. 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | News and advertising (a) | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | News and advertising (a) | Impact of ASU No. 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | Other (a) | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | Other (a) | Impact of ASU No. 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | Advertising and News [Member] | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Restatement Adjustment | Advertising and News [Member] | Impact of ASU No. 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Altice Technical Services | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											(1,105)
Programming and other direct costs											0
Other operating expenses											35,038
Restructuring and other expense											0
Depreciation and amortization (including impairments)											96
Operating income											(36,239)
Total other income (expense)											0
Loss before income taxes											(36,239)
Income tax benefit											9,385
Net income											(26,854)
Altice Technical Services | Restatement Adjustment | CSC Holdings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax benefit											9,973
Net income											(26,266)
Altice Technical Services | Restatement Adjustment | Video
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											(501)
Altice Technical Services | Restatement Adjustment | Broadband
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											(369)
Altice Technical Services | Restatement Adjustment | Telephony
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											(235)
Altice Technical Services | Restatement Adjustment | Business services and wholesale
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Altice Technical Services | Restatement Adjustment | News and advertising (a)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Altice Technical Services | Restatement Adjustment | Other (a)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Altice Technical Services | Restatement Adjustment | Advertising and News [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											0
Cequel Corp. | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											2,661,782
Programming and other direct costs											755,593
Other operating expenses											666,990
Restructuring and other expense											39,899
Depreciation and amortization (including impairments)											678,861
Operating income											520,439
Total other income (expense)											(180,526)
Loss before income taxes											339,913
Income tax benefit											584,062
Net income											923,975
Cequel Corp. | Restatement Adjustment | Video
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											1,101,507
Cequel Corp. | Restatement Adjustment | Broadband
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											960,757
Cequel Corp. | Restatement Adjustment | Telephony
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											130,503
Cequel Corp. | Restatement Adjustment | Business services and wholesale
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											375,656
Cequel Corp. | Restatement Adjustment | News and advertising (a)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											70,717
Cequel Corp. | Restatement Adjustment | Other (a)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenue											$ 22,642