FAIR VALUE MEASUREMENT - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	$ 24,010,192	$ 22,787,410
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	25,481,818	23,235,572
CSC Holdings | Credit facility debt | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	6,632,330	5,915,559
CSC Holdings | Credit facility debt | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	6,679,875	5,972,500
CSC Holdings | Collateralized indebtedness | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,423,519	1,406,182
CSC Holdings | Collateralized indebtedness | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,423,130	1,374,203
CSC Holdings | Senior guaranteed notes | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	7,600,412	5,847,758
CSC Holdings | Senior guaranteed notes | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	8,136,444	5,646,468
CSC Holdings | Senior notes and debentures | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	7,142,714	8,416,610
CSC Holdings | Senior notes and debentures | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	7,912,429	8,972,722
CSC Holdings | Notes payable and supply chain financing | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	110,519	106,108
CSC Holdings | Notes payable and supply chain financing | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	110,580	105,836
Cablevision Systems Corp. | Senior notes and debentures | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,100,698	1,095,193
Cablevision Systems Corp. | Senior notes and debentures | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	$ 1,219,360	$ 1,163,843