GOODWILL AND INTANGIBLE ASSETS - SCHEDULE OF GOODWILL BY REPORTING UNIT (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($) segment	Sep. 30, 2015 USD ($) segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Goodwill
Balance at the beginning of the period		$ 1,754,926	$ 1,754,926
Impairment			(14,056)	$ 0	$ 0
Balance at the end of the period	$ 2,245,364		2,245,364	1,754,926
Number of reportable segments | segment	6
Operating Segments
Goodwill
Balance at the beginning of the period		1,754,926	1,754,926	1,675,323
Additions			552,864	165,095
(Deductions)				(35,441)
Impairment			(14,056)
Foreign exchange translation			(48,370)	(50,051)
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			0
Balance at the end of the period	$ 2,245,364		2,245,364	1,754,926	1,675,323
Operating Segments | Search & Applications
Goodwill
Balance at the beginning of the period		$ 774,822	774,822	738,062
Additions			1,450	71,616
(Deductions)				(33,510)
Impairment			0
Foreign exchange translation			(1,230)	(1,346)
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			(775,042)
Balance at the end of the period	$ 0		0	774,822	738,062
Number of operating segments | segment		1
Number of reportable segments | segment		1
Number of operating segments after split | segment	3
Number of reportable segments after split | segment	3
Accumulated goodwill impairment loss				916,900	916,900
Operating Segments | Match Group
Goodwill
Balance at the beginning of the period		$ 791,474	791,474	768,080
Additions			547,910	72,833
(Deductions)				(1,931)
Impairment			0
Foreign exchange translation			(46,275)	(47,508)
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			0
Balance at the end of the period	$ 1,293,109		1,293,109	791,474	768,080
Operating Segments | HomeAdvisor
Goodwill
Balance at the beginning of the period		151,321	151,321	131,872
Additions			0	20,646
(Deductions)				0
Impairment			0
Foreign exchange translation			(1,070)	(1,197)
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			0
Balance at the end of the period	150,251		150,251	151,321	131,872
Operating Segments | Publishing
Goodwill
Balance at the beginning of the period		0	0	0
Additions			3,504	0
(Deductions)				0
Impairment			0
Foreign exchange translation			963	0
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			272,725
Balance at the end of the period	277,192		277,192	0	0
Accumulated goodwill impairment loss	322,600		322,600
Operating Segments | Applications
Goodwill
Balance at the beginning of the period		0	0	0
Additions			0	0
(Deductions)				0
Impairment			0
Foreign exchange translation			0	0
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			447,242
Balance at the end of the period	447,242		447,242	0	0
Accumulated goodwill impairment loss	529,100		529,100
Operating Segments | Video
Goodwill
Balance at the beginning of the period		15,590	15,590	15,590
Additions			0	0
(Deductions)				0
Impairment			0
Foreign exchange translation			0	0
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			0
Balance at the end of the period	15,590		15,590	15,590	15,590
Operating Segments | Video | Connected Ventures
Goodwill
Balance at the beginning of the period		8,267	8,267	8,267
Additions			0	0
(Deductions)				0
Impairment			0
Foreign exchange translation			0	0
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			0
Balance at the end of the period	8,267		8,267	8,267	8,267
Accumulated goodwill impairment loss	11,600		11,600
Operating Segments | Video | DailyBurn
Goodwill
Balance at the beginning of the period		7,323	7,323	7,323
Additions			0	0
(Deductions)				0
Impairment			0
Foreign exchange translation			0	0
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			0
Balance at the end of the period	7,323		7,323	7,323	7,323
Operating Segments | Other
Goodwill
Balance at the beginning of the period		21,719	21,719	21,719
Additions			0	0
(Deductions)				0
Impairment	(14,100)		(14,056)
Foreign exchange translation			(758)	0
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			55,075
Balance at the end of the period	61,980		61,980	21,719	21,719
Operating Segments | Other | ShoeBuy
Goodwill
Balance at the beginning of the period		21,719	21,719	21,719
Additions			0	0
(Deductions)				0
Impairment			(14,056)
Foreign exchange translation			0	0
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			0
Balance at the end of the period	7,663		7,663	21,719	21,719
Accumulated goodwill impairment loss	28,000		28,000	42,100
Operating Segments | Other | PriceRunner
Goodwill
Balance at the beginning of the period		$ 0	0	0
Additions			0	0
(Deductions)				0
Impairment			0
Foreign exchange translation			(758)	0
Allocation of IAC's former Search & Applications segment goodwill based on relative fair value			55,075
Balance at the end of the period	54,317		54,317	$ 0	$ 0
Accumulated goodwill impairment loss	$ 65,200		$ 65,200