CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Parent [Member]	Member's Equity (Deficiency)	Accumulated Deficit	Treasury Stock	Accumulated Other Comprehensive Income	Noncontrolling Interests	Common Class A Common Stock	Common Class B Common Stock
Beginning balance at Dec. 31, 2019	$ 2,279,262	$ 2,269,964	$ 2,039,918		$ (163,904)	$ (3,250)	$ 9,298	$ 4,572	$ 1,862
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to Altice USA, Inc. stockholders	(858)			$ (858)				(858)	0
Net loss (income) attributable to noncontrolling interests	680						680
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Plan Amendments, Net Of Tax	9,503	9,503				9,503
Foreign currency translation adjustment, net	(424)	(424)				(424)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	27,370	27,370	27,370
Redeemable equity vested	29,479	29,479	29,479
Adjustments to Additional Paid in Capital, Increase in Carrying Amount of Redeemable Preferred Stock	13,260	13,260	13,260
Class A shares acquired through share repurchase program and retired	(749,998)	(749,998)	(749,686)					(312)
Stock Issued During Period, Value, New Issues	2,507	2,507			11
Other							4,302
Ending balance at Mar. 31, 2020	1,590,415	1,581,797	1,362,836		(163,893)	(13,177)	8,618	4,261	1,862
Beginning balance at Dec. 31, 2020	(1,203,139)	(1,141,030)	0	(985,641)	(163,866)	3,646	(62,109)	2,972	1,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to Altice USA, Inc. stockholders	274,136	274,136		274,136
Net loss (income) attributable to noncontrolling interests	(4,403)						(4,403)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Plan Amendments, Net Of Tax	(6,356)	(6,356)				6,356
Foreign currency translation adjustment, net	619	619				619
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	27,964	27,964		27,964
Redeemable equity vested	20,131	20,131		20,131
Adjustments to Additional Paid in Capital, Increase in Carrying Amount of Redeemable Preferred Stock	2,528	2,528		2,528
Class A shares acquired through share repurchase program and retired	(522,673)	(522,673)		(522,521)				(152)
Conversion of Class B to Class A shares								1	(1)
Stock Issued During Period, Value, New Issues	2,044	2,044	2,495	2,037	6			1
Other	58	(4,244)	0	(4,244)
Ending balance at Mar. 31, 2021	$ (1,387,573)	$ (1,334,169)	$ 0	$ (1,185,610)	$ (163,860)	$ 10,621	$ (53,404)	$ 2,822	$ 1,858