INCOME TAXES - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
NOLs, capital loss, and tax credit carry forwards (a)	$ 129,444	$ 130,134
Compensation and benefit plans	61,486	90,853
Restructuring liability	2,349	7,220
Other liabilities	21,482	50,440
Deferred Tax Asset, In-Process Research and Development	40,872	33,427
Deferred Tax Liabilities, Derivatives	(9,745)	(40,357)
Derivative contracts	1,516	1,519
Interest deferred for tax purposes	781,826	536,284
Operating lease liability	74,773	79,263
Deferred tax assets	1,113,748	929,140
Less: Valuation allowance	(93,005)	(87,407)
Net deferred tax assets, noncurrent	1,020,743	841,733
Fixed assets and intangibles	(5,208,559)	(5,250,112)
Operating lease asset	(61,014)	(64,163)
Deferred Tax Assets, Investment in Subsidiaries	(185,473)	(173,198)
Prepaid expenses	(11,513)	(14,630)
Fair value adjustments related to debt and deferred financing costs	0	(1,751)
Opportunity Zone tax deferral	0	(145,655)
Deferred tax liability, noncurrent	(5,476,304)	(5,689,866)
Total net deferred tax liabilities	(4,455,561)	(4,848,133)
Carried back capital losses	98,207
Unrecognized Tax Benefits	114,365	53,010	$ 70,593	$ 25,296
CSC Holdings
NOLs, capital loss, and tax credit carry forwards (a)	109,103	104,071
Compensation and benefit plans	61,486	90,853
Restructuring liability	2,349	7,220
Other liabilities	21,482	50,440
Deferred Tax Asset, In-Process Research and Development	40,872	33,427
Deferred Tax Liabilities, Derivatives	(9,745)	(40,357)
Derivative contracts	1,516	1,519
Interest deferred for tax purposes	781,826	536,284
Operating lease liability	74,773	79,263
Deferred tax assets	1,093,407	903,077
Less: Valuation allowance	(72,664)	(64,844)
Net deferred tax assets, noncurrent	1,020,743	838,233
Fixed assets and intangibles	(5,208,559)	(5,250,112)
Operating lease asset	(61,014)	(64,163)
Deferred Tax Assets, Investment in Subsidiaries	(185,473)	(173,198)
Prepaid expenses	(11,513)	(14,630)
Fair value adjustments related to debt and deferred financing costs	0	(1,751)
Opportunity Zone tax deferral	0	(145,655)
Deferred tax liability, noncurrent	(5,476,304)	(5,689,866)
Total net deferred tax liabilities	$ (4,455,561)	$ (4,851,633)