CSC HOLDINGS - CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 220,571	$ 278,422
Restricted cash	264	264
Accounts receivable, trade (less allowance for doubtful accounts of $13,420 and $11,677)	376,155	442,581
Prepaid expenses and other current assets (including a prepayment to an affiliate of $19,563 in 2017) (See Note 14)	221,819	200,252
Amounts due from affiliates	3,795	4,262
Derivative contracts	8,252	50,785
Total current assets	830,856	976,566
Property, plant and equipment, net	5,843,572	5,805,996
Right-of-use operating lease assets	234,358	241,342
Investment securities pledged as collateral		2,250,854
Derivative contracts	0	4,774
Other assets	92,137	87,429
Amortizable intangible assets, net of accumulated amortization	2,616,017	2,781,116
Indefinite-lived cable television franchises	13,068,017	13,068,017
Goodwill	8,160,566	8,160,566
Total assets	33,169,831	33,376,660
Current Liabilities:
Accounts payable	879,032	795,576
Interest payable	233,968	252,060
Accrued employee related costs	104,220	142,116
Amounts due to affiliates	12,698	8,538
Deferred revenue	153,032	109,798
Debt	1,258,055	1,245,713
Other current liabilities	550,263	544,302
Total current liabilities	3,191,268	3,098,103
Other liabilities	172,766	192,563
Deferred tax liability	5,037,625	5,006,167
Liabilities under derivative contracts	472,402	523,150
Right-of-use operating lease liability	248,758	257,424
Long-term debt, net of current maturities	25,431,481	25,476,629
Total liabilities	34,554,300	34,554,036
Commitments and contingencies (Note 16)
Redeemable equity	3,104	25,763
Limited Liability Company (LLC) Members' Equity [Abstract]
Accumulated other comprehensive income (loss)	10,621	3,646
Noncontrolling interests	(53,404)	(62,109)
Total liabilities and stockholders' deficiency	33,169,831	33,376,660
Customer Relationships [Member]
Current Assets:
Amortizable intangible assets, net of accumulated amortization	2,433,901	2,573,856
Other Intangible Assets [Member]
Current Assets:
Amortizable intangible assets, net of accumulated amortization	18,853	20,366
CSC Holdings
Current Assets:
Cash and cash equivalents	220,214	277,938
Restricted cash	264	264
Accounts receivable, trade (less allowance for doubtful accounts of $13,420 and $11,677)	376,155	442,581
Prepaid expenses and other current assets (including a prepayment to an affiliate of $19,563 in 2017) (See Note 14)	221,819	200,252
Amounts due from affiliates	3,795	4,262
Derivative contracts	8,252	50,785
Total current assets	830,499	976,082
Property, plant and equipment, net	5,843,572	5,805,996
Right-of-use operating lease assets	234,358	241,342
Investment securities pledged as collateral	2,324,308	2,250,854
Derivative contracts	0	4,774
Other assets	92,137	87,429
Amortizable intangible assets, net of accumulated amortization	2,616,017	2,781,116
Indefinite-lived cable television franchises	13,068,017	13,068,017
Goodwill	8,160,566	8,160,566
Total assets	33,169,474	33,376,176
Current Liabilities:
Accounts payable	879,032	795,576
Interest payable	233,968	252,060
Accrued employee related costs	104,220	142,116
Amounts due to affiliates	12,698	8,538
Deferred revenue	153,032	109,798
Debt	1,258,055	1,245,713
Other current liabilities	530,853	543,834
Total current liabilities	3,171,858	3,097,635
Other liabilities	172,766	192,563
Deferred tax liability	5,065,438	5,033,980
Liabilities under derivative contracts	472,402	523,150
Right-of-use operating lease liability		257,424
Long-term debt, net of current maturities	25,431,481	25,476,629
Total liabilities	34,562,703	34,581,381
Redeemable equity	3,104	25,763
Limited Liability Company (LLC) Members' Equity [Abstract]
Membership interest before accumulated comprehensive loss	(1,353,550)	(1,172,505)
Accumulated other comprehensive income (loss)	10,621	3,646
Membership equity before noncontrolling interest	(1,342,929)	(1,168,859)
Noncontrolling interests	(53,404)	(62,109)
Total Equity (Deficiency)	(1,396,333)	(1,230,968)
Total liabilities and stockholders' deficiency	$ 33,169,474	$ 33,376,176