CSC HOLDINGS - CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($)	3 Months Ended					12 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 1,331,000	$ (25,198,000)	$ 213,808,000	$ (128,949,000)		$ 139,939,000	$ 20,594,000	$ 1,494,764,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation, Depletion and Amortization						2,263,144,000	2,382,339,000	2,930,571,000
Equity in net loss of affiliates						0	10,849,000	10,040,000
Gain (Loss) on Investments And Sale Of Affiliated Interests						(473,406,000)	250,877,000	(237,354,000)
Loss (gain) on equity derivative contracts, net						282,713,000	(218,848,000)	236,330,000
Loss on extinguishment of debt and write-off of deferred financing costs						243,806,000	48,804,000	600,240,000
Amortization of deferred financing costs and discounts (premiums) on indebtedness						106,214,000	85,121,000	31,046,000
Share-based compensation expense related to equity classified awards						99,078,000	59,812,000	57,430,000
Deferred income taxes						14,931,000	(67,603,000)	(2,880,154,000)
Provision for doubtful accounts						91,520,000	71,426,000	74,183,000
Change in assets and liabilities, net of effects of acquisitions and dispositions:
Accounts receivable, trade						(91,718,000)	(144,079,000)	(89,683,000)
Other receivables						(21,755,000)	4,246,000	(12,835,000)
Prepaid expenses and other assets						(100,343,000)	(14,889,000)	(7,426,000)
Amounts due from and due to affiliates						(7,857,000)	11,049,000	(34,326,000)
Accounts payable						(33,107,000)	12,455,000	73,888,000
Accrued liabilities						(44,083,000)	(130,631,000)	(241,701,000)
Deferred revenue						(10,384,000)	72,426,000	12,310,000
Liabilities related to interest rate swap and derivative contracts						30,338,000	53,101,000	(921,000)
Net cash provided by operating activities						2,554,169,000	2,508,317,000	2,018,247,000
Cash flows from investing activities:
Capital expenditures						(1,355,350,000)	(1,153,589,000)	(951,349,000)
Payment for acquisitions, net of cash acquired						(172,269,000)	(10,753,000)	(46,703,000)
Sale of affiliate interest						1,958,000		0
Sale of affiliate interest							3,537,000
Proceeds related to sale of equipment, including costs of disposal						3,909,000	10,779,000	9,743,000
Decrease (increase) in other investments						354,000	9,327,000	(4,773,000)
Settlement of put call options						0	0	97,410,000
Additions to other intangible assets						(4,071,000)	(584,000)	(1,707,000)
Net cash used in investing activities						(1,525,469,000)	(1,148,357,000)	(1,092,199,000)
Cash flows from financing activities:
Proceeds from credit facility debt, net of discounts						5,040,000,000	3,489,313,000	5,593,675,000
Repayment of credit facility debt						(3,832,062,000)	(2,221,175,000)	(4,411,581,000)
Proceeds from issuance of senior notes						4,054,375,000	2,050,000,000	0
Redemption of senior notes, including premiums and fees						(4,225,786,000)	(2,628,962,000)	(1,729,400,000)
Proceeds from collateralized indebtedness						93,000,000	516,513,000	838,794,000
Repayment of collateralized indebtedness and related derivative contracts, net						0	(516,513,000)	(831,059,000)
Payments of dividends					$ 79,617,000	0	1,499,935,000	919,317,000	$ 365,559,000
Proceeds from Contributed Capital						0	0	1,135,000
Proceeds from notes payable						65,854,000	15,955,000	33,733,000
Repayment of notes payable						(102,066,000)	(32,632,000)	0
Principal payments on finance lease obligations						(8,980,000)	(10,228,000)	(15,157,000)
Additions to deferred financing costs						(23,583,000)	(28,468,000)	(8,600,000)
Contingent payment for acquisition						(500,000)	(30,000,000)	0
Proceeds from (Payments to) Noncontrolling Interests						(1,000,000)	5,995,000	(335,000)
Net cash used in financing activities						(624,412,000)	(1,390,996,000)	(1,099,041,000)
Net increase (decrease) in cash and cash equivalents						404,288,000	(31,036,000)	(172,993,000)
Effect of exchange rate changes on cash and cash equivalents						(1,166,000)	(26,000)	0
Net increase (decrease) in cash and cash equivalents						403,122,000	(31,062,000)	(172,993,000)
Cash, cash equivalents and restricted cash at beginning of year		299,038,000		330,100,000	503,093,000	299,038,000	330,100,000	503,093,000
Cash, cash equivalents and restricted cash at end of year	702,160,000		299,038,000			702,160,000	299,038,000	330,100,000	503,093,000
Restructuring Reserve, Settled without Cash						16,826,000	0	0
Non-cash lease expense						46,581,000	0	0
CSC Holdings
Cash flows from operating activities:
Net income	21,022,000	(7,864,000)	242,020,000	(89,968,000)		212,817,000	260,326,000	2,577,876,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation, Depletion and Amortization						2,263,144,000	2,382,339,000	2,930,571,000
Equity in net loss of affiliates						0	10,849,000	10,040,000
Gain (Loss) on Investments And Sale Of Affiliated Interests						(473,406,000)	261,536,000	(237,354,000)
Loss (gain) on equity derivative contracts, net						282,713,000	(218,848,000)	138,920,000
Loss on extinguishment of debt and write-off of deferred financing costs						228,130,000	7,883,000	53,988,000
Amortization of deferred financing costs and discounts (premiums) on indebtedness						90,706,000	43,135,000	13,226,000
Settlement loss and amortization of actuarial losses related to pension and postretirement plans						1,732,000	1,268,000	1,845,000
Share-based compensation expense related to equity classified awards						99,078,000	59,812,000	57,430,000
Deferred income taxes						(238,709,000)	(251,593,000)	(3,026,782,000)
Provision for doubtful accounts						91,520,000	71,426,000	74,183,000
Change in assets and liabilities, net of effects of acquisitions and dispositions:
Accounts receivable, trade						(91,718,000)	(144,079,000)	(89,683,000)
Other receivables						(12,512,000)	4,048,000	(12,707,000)
Prepaid expenses and other assets						(100,343,000)	(27,986,000)	(12,135,000)
Amounts due from and due to affiliates						247,917,000	175,159,000	(413,930,000)
Accounts payable						(33,107,000)	12,455,000	73,888,000
Accrued liabilities						(27,581,000)	(7,182,000)	(97,154,000)
Deferred revenue						(10,384,000)	72,426,000	20,634,000
Liabilities related to interest rate swap and derivative contracts						30,338,000	53,101,000	(921,000)
Net cash provided by operating activities						2,623,742,000	2,766,075,000	2,061,935,000
Cash flows from investing activities:
Capital expenditures						(1,355,350,000)	(1,153,589,000)	(951,349,000)
Payment for acquisitions, net of cash acquired						(172,269,000)	(10,753,000)	(46,703,000)
Sale of affiliate interest						1,958,000		0
Sale of affiliate interest							3,537,000
Proceeds related to sale of equipment, including costs of disposal						3,909,000	10,779,000	9,743,000
Decrease (increase) in other investments						354,000	(2,500,000)	(4,773,000)
Additions to other intangible assets						(4,071,000)	(584,000)	(1,707,000)
Net cash used in investing activities						(1,525,469,000)	(1,160,184,000)	(994,789,000)
Cash flows from financing activities:
Proceeds from credit facility debt, net of discounts						5,040,000,000	3,489,313,000	5,593,675,000
Repayment of credit facility debt						(3,832,062,000)	(2,221,175,000)	(4,411,581,000)
Proceeds from issuance of senior notes						4,054,375,000	1,000,000,000	0
Redemption of senior notes, including premiums and fees						(3,703,454,000)	(805,206,000)	(350,120,000)
Proceeds from collateralized indebtedness						93,000,000	516,513,000	838,794,000
Repayment of collateralized indebtedness and related derivative contracts, net						0	(516,513,000)	(831,059,000)
Payments of dividends						2,279,472,000	3,058,750,000	2,777,497,000
Proceeds from Contributed Capital						0	50,000,000	761,316,000
Proceeds from notes payable						65,854,000	15,955,000	33,733,000
Repayment of notes payable						(102,066,000)	(32,632,000)	0
Principal payments on finance lease obligations						(8,980,000)	(10,228,000)	(15,157,000)
Additions to deferred financing costs						(23,583,000)	(28,471,000)	(8,171,000)
Contingent payment for acquisition						(500,000)	(30,000,000)	0
Proceeds from (Payments to) Noncontrolling Interests						(1,000,000)	5,995,000	(335,000)
Net cash used in financing activities						(697,888,000)	(1,625,199,000)	(1,166,402,000)
Net increase (decrease) in cash and cash equivalents						400,385,000	(19,308,000)	(99,256,000)
Effect of exchange rate changes on cash and cash equivalents						(1,166,000)	(26,000)	0
Net increase (decrease) in cash and cash equivalents						399,219,000	(19,334,000)	(99,256,000)
Cash, cash equivalents and restricted cash at beginning of year		$ 298,784,000		$ 318,118,000	$ 417,374,000	298,784,000	318,118,000	417,374,000
Cash, cash equivalents and restricted cash at end of year	$ 698,003,000		$ 298,784,000			698,003,000	298,784,000	318,118,000	$ 417,374,000
Restructuring Reserve, Settled without Cash						16,826,000	0	0
Non-cash lease expense						$ 46,581,000	$ 0	$ 0