ACCUMULATED OTHER COMPREHENSIVE LOSS - Summary (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Loss
Balance at beginning of period			$ 2,928,042,000
Other comprehensive income			13,997,000	$ (16,303,000)
Amounts reclassified into earnings			(168,000)
Net period other comprehensive loss			13,829,000	(16,303,000)
Allocation of accumulated other comprehensive income (loss) related to the noncontrolling interests			628,000	421,000
Separation of IAC			13,781,000
Balance at end of period	$ (1,442,934,000)		(1,442,934,000)
Tax benefit / provision in accumulated other comprehensive loss	0	$ 0	0	0
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Loss
Balance at beginning of period	(124,312,000)	(125,705,000)	(136,349,000)	(128,722,000)
Other comprehensive income	16,205,000	(18,389,000)
Amounts reclassified into earnings	(4,000)
Net period other comprehensive loss	16,201,000	(18,389,000)
Allocation of accumulated other comprehensive income (loss) related to the noncontrolling interests		(510,000)
Balance at end of period	(108,111,000)	(144,604,000)	(108,111,000)	(144,604,000)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Loss
Balance at beginning of period			(136,349,000)	(128,726,000)
Other comprehensive income			13,998,000	(16,299,000)
Amounts reclassified into earnings			(168,000)
Net period other comprehensive loss			13,830,000	(16,299,000)
Allocation of accumulated other comprehensive income (loss) related to the noncontrolling interests			628,000	421,000
Separation of IAC			13,780,000
Balance at end of period	(108,111,000)	(144,604,000)	(108,111,000)	(144,604,000)
Unrealized Gain (Loss) on Available-For-Sale Security
Accumulated Other Comprehensive Loss
Balance at beginning of period			0	4,000
Other comprehensive income			(1,000)	(4,000)
Amounts reclassified into earnings			0
Net period other comprehensive loss			(1,000)	(4,000)
Allocation of accumulated other comprehensive income (loss) related to the noncontrolling interests			0	0
Separation of IAC			1,000
Balance at end of period	$ 0	$ 0	$ 0	$ 0