DEBT - Credit Silo Combination (Details) - USD ($)	1 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal amount		$ 26,917,870,000	$ 26,940,911,000
Long-term debt		26,771,563,000	26,722,342,000
Face Amount of Senior Notes and Senior Guaranteed Notes		7,660,000,000	7,658,806,000
Carrying amount of Senior Notes and Senior Guaranteed Notes		7,634,946,000	7,626,309,000
Face amount of Credit Facility Debt		7,220,625,000	7,750,188,000
Carrying value of Credit Facility Debt		7,182,379,000	7,705,192,000
Finance Lease, Liability		207,088,000	159,637,000
Debt		1,889,730,000	1,245,713,000
Finance Lease, Liability, Current		99,334,000	63,454,000
Long-term debt, net of current maturities		24,881,833,000	25,476,629,000
Principal Amount		26,917,870,000	26,940,911,000
Face Amount of Senior Notes		8,524,024,000	8,024,024,000
Carrying amount of Senior Notes		8,534,982,000	8,009,426,000
Senior Notes, Current		(1,629,128,000)	(989,917,000)
Cablevision Lightpath
Debt Instrument [Line Items]
Face Amount of Senior Notes and Senior Secured Notes		1,460,500,000	1,465,000,000
Carrying amount of Senior Notes and Senior Secured Notes		1,428,317,000	1,429,471,000
Loans Payable
Debt Instrument [Line Items]
Principal amount		82,518,000	113,592,000
Long-term debt		82,518,000	113,592,000
Principal Amount		82,518,000	113,592,000
Credit Facility [Domain]
Debt Instrument [Line Items]
Principal amount		78,750,000	78,750,000
Debt		78,750,000	78,750,000
Principal Amount		78,750,000	78,750,000
Short-term Debt
Debt Instrument [Line Items]
Principal amount		1,909,626,000	1,255,796,000
Debt		1,889,730,000	1,245,713,000
Principal Amount		1,909,626,000	1,255,796,000
Senior Notes
Debt Instrument [Line Items]
Principal amount		1,649,024,000	1,000,000,000
Principal Amount		1,649,024,000	1,000,000,000
Incremental Term Loan B-3 | Secured Debt [Member]
Debt Instrument [Line Items]
Principal amount		$ 1,243,125,000	1,252,688,000
Stated interest rate		2.334%
Credit facility		$ 1,239,366,000	1,248,293,000
Principal Amount		1,243,125,000	1,252,688,000
CSC Holdings Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Principal amount		$ 150,000,000	625,000,000
Stated interest rate		2.334%
Line of Credit Facility, Maximum Borrowing Capacity		$ 2,475,000,000
Credit facility		143,141,000	616,027,000
Principal Amount		$ 150,000,000	625,000,000
CSC Holdings Revolving Credit Facility | Secured Debt [Member] | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		2.25%
CSC Holdings Term Loan B | Secured Debt [Member]
Debt Instrument [Line Items]
Principal amount		$ 2,872,500,000	2,895,000,000
Stated interest rate		2.334%
Credit facility		$ 2,863,325,000	2,884,065,000
Principal Amount		2,872,500,000	2,895,000,000
Incremental Term Loan B-5 | Secured Debt [Member]
Debt Instrument [Line Items]
Principal amount		$ 2,955,000,000	2,977,500,000
Stated interest rate		2.584%
Credit facility		$ 2,936,547,000	2,956,807,000
Principal Amount		2,955,000,000	2,977,500,000
Secured Debt [Member]
Debt Instrument [Line Items]
Principal amount		1,759,017,000	1,699,566,000
Long-term debt		1,697,235,000	1,617,506,000
Principal Amount		1,759,017,000	1,699,566,000
Loans Payable
Debt Instrument [Line Items]
Principal amount		86,616,000	183,690,000
Long-term debt		86,616,000	174,801,000
Principal Amount		86,616,000	183,690,000
Cablevision Lightpath Term B Loan | Secured Debt [Member]
Debt Instrument [Line Items]
Principal amount		$ 595,500,000	600,000,000
Stated interest rate		3.75%
Line of Credit Facility, Maximum Borrowing Capacity		$ 100,000,000
Credit facility		580,033,000	582,808,000
Principal Amount		595,500,000	600,000,000
Cablevision Lightpath Term B Loan | Secured Debt [Member] | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate	3.25%
Cablevision Lightpath Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Principal amount		0	0
Credit facility		0	0
Principal Amount		0	0
Senior Notes | 8.0% Notes due April 15, 2020
Debt Instrument [Line Items]
Principal amount		$ 1,000,000,000	1,000,000,000
Stated interest rate		3.375%
Outstanding debt		$ 996,899,000	996,692,000
Principal Amount		1,000,000,000	1,000,000,000
Senior Notes | 6.75% Notes due November 15, 2021
Debt Instrument [Line Items]
Principal amount		$ 1,000,000,000	1,000,000,000
Stated interest rate		6.75%
Outstanding debt		$ 998,502,000	989,917,000
Principal Amount		1,000,000,000	1,000,000,000
Senior Notes | 5.875% Notes due September 15, 2022
Debt Instrument [Line Items]
Principal amount		$ 649,024,000	649,024,000
Stated interest rate		5.875%
Outstanding debt		$ 630,626,000	617,333,000
Principal Amount		649,024,000	649,024,000
Senior Notes | 5.25% Notes due June 1, 2024
Debt Instrument [Line Items]
Principal amount		$ 750,000,000	750,000,000
Stated interest rate		5.25%
Outstanding debt		$ 707,483,000	697,041,000
Principal Amount		750,000,000	750,000,000
Senior Notes | Cablevision 7.500% Notes due April 1, 2028
Debt Instrument [Line Items]
Principal amount		$ 4,118,000	4,118,000
Stated interest rate		7.50%
Outstanding debt		$ 4,113,000	4,112,000
Principal Amount		4,118,000	4,118,000
Senior Notes | CSC Holdings 7.500% Notes due April 1, 2028
Debt Instrument [Line Items]
Principal amount		$ 1,045,882,000	1,045,882,000
Stated interest rate		7.50%
Outstanding debt		$ 1,044,540,000	1,044,424,000
Principal Amount		1,045,882,000	1,045,882,000
Senior Notes | CSC Holdings 5.750% Notes due January 15, 2030
Debt Instrument [Line Items]
Principal amount		$ 2,250,000,000	2,250,000,000
Stated interest rate		5.75%
Outstanding debt		$ 2,283,702,000	2,286,097,000
Principal Amount		2,250,000,000	2,250,000,000
Senior Notes | CSC Holdings 4.625% Notes due December 1, 2030
Debt Instrument [Line Items]
Principal amount		$ 2,325,000,000	2,325,000,000
Stated interest rate		4.625%
Outstanding debt		$ 2,367,815,000	2,370,502,000
Principal Amount		2,325,000,000	2,325,000,000
Senior Notes | Cablevision Lightpath LLC 5.625% Notes due September 15, 2028
Debt Instrument [Line Items]
Principal amount		$ 415,000,000	415,000,000
Stated interest rate		5.625%
Outstanding debt		$ 406,865,000	406,176,000
Principal Amount		415,000,000	415,000,000
Senior Notes | CSC Holdings 5.000% Notes due November 15, 2031
Debt Instrument [Line Items]
Principal amount		$ 500,000,000
Stated interest rate		5.00%
Outstanding debt		$ 498,201,000
Principal Amount		500,000,000
Senior Notes | CSC Holdings 4.500% Senior Guaranteed Notes due November 15, 2021
Debt Instrument [Line Items]
Principal amount		$ 1,500,000,000
Stated interest rate		4.50%
Outstanding debt		$ 1,494,604,000
Principal Amount		1,500,000,000
Secured Debt [Member] | CSC Holdings 5.500% Notes due May 15, 2026
Debt Instrument [Line Items]
Principal amount		$ 0	1,498,806,000
Stated interest rate		5.50%
Outstanding debt		$ 0	1,487,644,000
Principal Amount		0	1,498,806,000
Secured Debt [Member] | 5.5% Notes due April 15, 2027
Debt Instrument [Line Items]
Principal amount		$ 1,310,000,000	1,310,000,000
Stated interest rate		5.50%
Outstanding debt		$ 1,306,365,000	1,305,955,000
Principal Amount		1,310,000,000	1,310,000,000
Secured Debt [Member] | 5.375% Senior Guaranteed Notes Due February 1, 2028
Debt Instrument [Line Items]
Principal amount		$ 1,000,000,000	1,000,000,000
Stated interest rate		5.375%
Outstanding debt		$ 994,064,000	993,490,000
Principal Amount		1,000,000,000	1,000,000,000
Secured Debt [Member] | CSC Holdings 6.500% Notes due February 1, 2029
Debt Instrument [Line Items]
Principal amount		$ 1,750,000,000	1,750,000,000
Stated interest rate		6.50%
Outstanding debt		$ 1,747,442,000	1,747,245,000
Principal Amount		1,750,000,000	1,750,000,000
Secured Debt [Member] | CSC Holdings 4.125% Notes due December 1, 2030
Debt Instrument [Line Items]
Principal amount		$ 1,100,000,000	1,100,000,000
Stated interest rate		4.125%
Outstanding debt		$ 1,095,572,000	1,095,283,000
Principal Amount		1,100,000,000	1,100,000,000
Secured Debt [Member] | Cablevision Lightpath LLC 3.875% Notes due September 15, 2027
Debt Instrument [Line Items]
Principal amount		$ 450,000,000	450,000,000
Stated interest rate		3.875%
Outstanding debt		$ 441,419,000	440,487,000
Principal Amount		450,000,000	450,000,000
Long-term Debt
Debt Instrument [Line Items]
Principal amount		25,008,244,000	25,685,115,000
Long-term debt, net of current maturities		24,881,833,000	25,476,629,000
Principal Amount		$ 25,008,244,000	$ 25,685,115,000