FAIR VALUE MEASUREMENT - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	$ 22,985,277	$ 21,919,331
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	23,699,331	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	4,435,479	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	4,470,000	3,435,000
CSC Holdings | Collateralized indebtedness | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,392,648	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	1,338,105	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	3,283,795	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	3,195,375	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	6,107,472	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	6,727,849	7,221,846
CSC Holdings | Notes payable | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	36,161	56,956
CSC Holdings | Notes payable | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	35,962	55,289
Cablevision | Senior notes and debentures | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,072,340	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	1,165,034	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	1,244,153	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	1,252,350	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	2,804,435	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	2,942,800	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	36,356	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	36,356	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	2,572,438	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	$ 2,535,500	$ 2,658,930