SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) vote shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)
Class of Stock [Line Items]
Advertising costs			$ 233,326	$ 240,273	$ 224,120
Cash distributions to shareholders	$ 839,700			1,499,935	840,035	$ 445,176
Payments of dividends		$ 79,617	$ 0	$ 1,499,935	$ 919,317	$ 365,559
Antidilutive securities | shares			4,245,000	6,292,000	14,000
Concentration Risk, Customer			10
Document Period End Date			Dec. 31, 2019
concentration of customer to trade receivables			10.00%
CSC Holdings
Class of Stock [Line Items]
Membership units outstanding | shares			100
Cash distributions to shareholders				$ 3,058,747	$ 2,777,498
Payments of dividends			$ 2,279,472	3,058,750	2,777,497
Distribution Made to Limited Liability Company (LLC) Member, Non-cash Distributions Paid			$ 2,279,472	(3,058,747)
Common Class A
Class of Stock [Line Items]
Common stock number of votes per share | vote			1
Common Class B
Class of Stock [Line Items]
Common stock number of votes per share | vote			25
Common stock conversion ratio			1
Minimum | Customer Contracts
Class of Stock [Line Items]
Finite-lived intangible asset, useful life			3 years
Maximum | Customer Contracts
Class of Stock [Line Items]
Finite-lived intangible asset, useful life			5 years
Franchise
Class of Stock [Line Items]
Franchise fees and other taxes and fees			$ 254,227	$ 257,467	$ 259,075