FAIR VALUE MEASUREMENT - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	$ 23,054,720	$ 21,919,331
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	24,059,171	23,279,472
CSC Holdings | Credit facility debt | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	4,980,221	3,393,306
CSC Holdings | Credit facility debt | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	5,033,750	3,435,000
CSC Holdings | Collateralized indebtedness | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,400,398	1,349,474
CSC Holdings | Collateralized indebtedness | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,352,771	1,305,932
CSC Holdings | Senior guaranteed notes | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	3,284,419	2,291,185
CSC Holdings | Senior guaranteed notes | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	3,293,125	2,420,000
CSC Holdings | Senior notes and debentures | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	5,610,048	6,409,889
CSC Holdings | Senior notes and debentures | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	6,245,760	7,221,846
CSC Holdings | Notes payable | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	42,810	56,956
CSC Holdings | Notes payable | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	42,653	55,289
Cablevision | Senior notes and debentures | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,076,681	1,818,115
Cablevision | Senior notes and debentures | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,189,098	1,931,239
Cequel Corp. [Member] | Credit facility debt | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,241,272	1,250,217
Cequel Corp. [Member] | Credit facility debt | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,249,188	1,258,675
Cequel Corp. [Member] | Senior notes and debentures | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	2,811,167	2,770,737
Cequel Corp. [Member] | Senior notes and debentures | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	3,013,615	2,983,615
Cequel Corp. [Member] | Notes payable | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	34,281	8,946
Cequel Corp. [Member] | Notes payable | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	34,281	8,946
Cequel Corp. [Member] | Senior secured notes | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	2,573,423	2,570,506
Cequel Corp. [Member] | Senior secured notes | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	$ 2,604,930	$ 2,658,930