DERIVATIVE CONTRACTS AND COLLATERALIZED INDEBTEDNESS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative [Line Items]
Gain (loss) on derivative contracts related to change in the value of equity derivative contracts related to Comcast common stock	$ 43,385	$ (261,597)	$ (109,020)	$ 26,203
Change in the fair value of Comcast common stock included in gain (loss) on investments	(46,821)	312,714	151,632	55,412
Gain (loss) on interest rate swap contracts, net of a gain of $74,835 recorded in the nine months 2020 period in connection with the early termination of the swap agreements discussed below	5,521	(158)	59,600	(88,725)
Notes related to derivative contracts
Derivative [Line Items]
Gain (loss) on derivative contracts related to change in the value of equity derivative contracts related to Comcast common stock	$ 43,385	$ (261,597)	$ (109,020)	$ 26,203

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