FAIR VALUE MEASUREMENT - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	$ 24,350,865	$ 22,787,410
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	25,892,634	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	7,148,287	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	7,190,438	5,972,500
CSC Holdings | Collateralized indebtedness | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,585,088	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	1,611,095	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	7,602,456	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	8,220,518	5,646,468
CSC Holdings | Senior notes | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	7,874,040	8,416,610
CSC Holdings | Senior notes | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	8,728,870	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	140,994	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	141,713	105,836
Cablevision Systems Corp. | Senior notes | Carrying Amount | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	0	1,095,193
Cablevision Systems Corp. | Senior notes | Estimated Fair Value | Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	$ 0	$ 1,163,843