EQUITY PLANS, Stock Option Award Activity (Details) (Cablevision Systems Corporation Employee Stock Plan, USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015		Dec. 31, 2014
Stock Options Outstanding, Weighted Average Exercise Price [Roll Forward]
Balance at beginning of period, weighted average exercise price per share (in dollars per share)	$ 14.41
Granted, weighted average exercise price per share (in dollars per share)	$ 19.17
Exercised, weighted average exercise price per share (in dollars per share)	$ 12.74
Balance at end of period, weighted average exercise price per share (in dollars per share)	$ 15.08		$ 14.41
Options exercisable at end of period, weighted average exercise price per share (in dollars per share)	$ 13.79
Options expected to vest in the future, weighted average exercise price per share (in dollars per share)	$ 16.93
Stock Options Outstanding, Additional Disclosures [Abstract]
Balance at beginning of period, weighted average remaining contractual term	7 years 4 months 17 days		7 years 2 months 0 days
Balance at end of period, weighted average remaining contractual term	7 years 4 months 17 days		7 years 2 months 0 days
Options exercisable at end of period, weighted average remaining contractual term	6 years 3 months 15 days
Options expected to vest in the future, weighted average remaining contractual term	8 years 11 months 5 days
Balance at beginning of period, aggregate intrinsic value	$ 79,347	[1]
Balance at end of period, aggregate intrinsic value	48,657	[1]	79,347	[1]
Options exercisable at end of period, aggregate intrinsic value	38,697	[1]
Options expected to vest in the future, aggregate intrinsic value	$ 9,960	[1]
Time Vesting Options
Stock Options Outstanding [Roll Forward]
Balance at beginning of period (in shares)	5,097,666
Granted (in shares)	2,000,000
Exercised (in shares)	(138,000)
Balance at end of period (in shares)	6,959,666
Options exercisable at end of period (in shares)	959,666
Options expected to vest in the future (in shares)	6,000,000
Performance Based Vesting Options
Stock Options Outstanding [Roll Forward]
Balance at beginning of period (in shares)	7,633,500
Granted (in shares)	0
Exercised (in shares)	(51,500)
Balance at end of period (in shares)	7,582,000
Options exercisable at end of period (in shares)	7,582,000
Options expected to vest in the future (in shares)	0
Stock Options | AMC Networks Inc. and Madison Square Garden
Stock Options Outstanding [Roll Forward]
Balance at end of period (in shares)	135,066

[1] The aggregate intrinsic value is calculated as the difference between (i) the exercise price of the underlying award and (ii) the quoted price of CNYG Class A common stock on March 31, 2015 or December 31, 2014, as indicated, and March 31, 2015 in the case of options exercisable and options expected to vest in the future.