GUARANTOR AND NONGUARANTOR FINANCIAL INFORMATION - CONDENSED STATEMENT OF OPERATIONS (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Statements of Operations
Revenue	$ 848,728	$ 838,561	$ 771,132	$ 772,512	$ 830,754	$ 782,231	$ 756,315	$ 740,247	$ 3,230,933	$ 3,109,547	$ 3,022,987
Cost of revenue	214,084	199,377	177,963	186,737	233,712	218,452	205,295	202,745	778,161	860,204	977,357
Selling and marketing expense									1,345,576	1,147,409	982,774
General and administrative expense									525,629	443,610	378,142
Product development expense									185,766	160,515	139,759
Depreciation									62,205	61,156	58,909
Amortization of intangibles									139,952	57,926	59,843
Goodwill impairment									14,056	0	0
Total operating costs and expenses									3,051,345	2,730,820	2,596,784
Operating income	(5,430)	87,130	62,769	35,119	110,372	100,953	95,690	71,712	179,588	378,727	426,203
Equity in earnings (losses) of unconsolidated affiliates									772	(9,697)	(6,615)
Interest expense									(73,636)	(56,314)	(33,596)
Other income (expense), net									36,149	(42,787)	30,309
Earnings from continuing operations before income taxes									142,873	269,929	416,301
Income tax provision									(29,516)	(35,372)	(134,502)
Earnings from continuing operations	(31,417)	65,026	57,885	21,863	67,986	150,261	(17,995)	34,305	113,357	234,557	281,799
Less: earnings from discontinued operations, net of tax	28	17	(153)	125	625	175,730	(868)	(814)	17	174,673	1,926
Net earnings	(31,389)	65,043	57,732	21,988	68,611	325,991	(18,863)	33,491	113,374	409,230	283,725
Net loss attributable to noncontrolling interests									6,098	5,643	2,059
Net earnings attributable to IAC shareholders	$ (31,849)	$ 65,611	$ 59,305	$ 26,405	$ 70,172	$ 326,812	$ (17,996)	$ 35,885	119,472	414,873	285,784
Comprehensive income attributable to IAC shareholders									55,069	340,219	304,907
Inter-segment Elimination
Condensed Statements of Operations
Revenue									(10,009)	(11,839)	(4,115)
Cost of revenue									(1,190)	(2,753)	(2,860)
Selling and marketing expense									(8,860)	(8,303)	(1,133)
General and administrative expense									41	45	(122)
Product development expense									0	(828)	0
Depreciation									0	0	0
Amortization of intangibles									0	0	0
Goodwill impairment									0
Total operating costs and expenses									(10,009)	(11,839)	(4,115)
Operating income									0	0	0
Equity in earnings (losses) of unconsolidated affiliates									(229,371)	(257,290)	(484,856)
Interest expense									0	0	0
Other income (expense), net									0	0	0
Earnings from continuing operations before income taxes									(229,371)	(257,290)	(484,856)
Income tax provision									0	0	0
Earnings from continuing operations									(229,371)	(257,290)	(484,856)
Less: earnings from discontinued operations, net of tax									12	(570)	39
Net earnings									(229,359)	(257,860)	(484,817)
Net loss attributable to noncontrolling interests									0	0	0
Net earnings attributable to IAC shareholders									(229,359)	(257,860)	(484,817)
Comprehensive income attributable to IAC shareholders									(160,053)	(178,155)	(496,381)
IAC
Condensed Statements of Operations
Revenue									0	0	0
Cost of revenue									720	998	2,456
Selling and marketing expense									3,210	2,138	2,563
General and administrative expense									93,090	105,221	97,025
Product development expense									4,311	6,496	4,685
Depreciation									1,918	1,426	1,386
Amortization of intangibles									0	0	0
Goodwill impairment									0
Total operating costs and expenses									103,249	116,279	108,115
Operating income									(103,249)	(116,279)	(108,115)
Equity in earnings (losses) of unconsolidated affiliates									215,462	253,582	439,925
Interest expense									(49,405)	(51,988)	(29,417)
Other income (expense), net									(3,571)	2,688	(35,331)
Earnings from continuing operations before income taxes									59,237	88,003	267,062
Income tax provision									60,218	152,197	16,796
Earnings from continuing operations									119,455	240,200	283,858
Less: earnings from discontinued operations, net of tax									17	174,673	1,926
Net earnings									119,472	414,873	285,784
Net loss attributable to noncontrolling interests									0	0	0
Net earnings attributable to IAC shareholders									119,472	414,873	285,784
Comprehensive income attributable to IAC shareholders									55,069	340,219	304,907
Guarantor Subsidiaries
Condensed Statements of Operations
Revenue									1,704,841	1,694,844	1,660,113
Cost of revenue									367,704	438,729	537,948
Selling and marketing expense									852,173	715,646	591,543
General and administrative expense									178,861	148,026	127,731
Product development expense									93,769	83,216	77,153
Depreciation									27,890	26,182	27,609
Amortization of intangibles									104,180	33,587	37,890
Goodwill impairment									14,056
Total operating costs and expenses									1,638,633	1,445,386	1,399,874
Operating income									66,208	249,458	260,239
Equity in earnings (losses) of unconsolidated affiliates									13,477	(6,440)	38,619
Interest expense									(6,130)	(4,229)	(3,957)
Other income (expense), net									28,077	12,533	(18,653)
Earnings from continuing operations before income taxes									101,632	251,322	276,248
Income tax provision									(36,425)	(98,198)	(81,803)
Earnings from continuing operations									65,207	153,124	194,445
Less: earnings from discontinued operations, net of tax									0	0	0
Net earnings									65,207	153,124	194,445
Net loss attributable to noncontrolling interests									0	0	0
Net earnings attributable to IAC shareholders									65,207	153,124	194,445
Comprehensive income attributable to IAC shareholders									61,730	144,926	195,308
Non-Guarantor Subsidiaries
Condensed Statements of Operations
Revenue									1,536,101	1,426,542	1,366,989
Cost of revenue									410,927	423,230	439,813
Selling and marketing expense									499,053	437,928	389,801
General and administrative expense									253,637	190,318	153,508
Product development expense									87,686	71,631	57,921
Depreciation									32,397	33,548	29,914
Amortization of intangibles									35,772	24,339	21,953
Goodwill impairment									0
Total operating costs and expenses									1,319,472	1,180,994	1,092,910
Operating income									216,629	245,548	274,079
Equity in earnings (losses) of unconsolidated affiliates									1,204	451	(303)
Interest expense									(18,101)	(97)	(222)
Other income (expense), net									11,643	(58,008)	84,293
Earnings from continuing operations before income taxes									211,375	187,894	357,847
Income tax provision									(53,309)	(89,371)	(69,495)
Earnings from continuing operations									158,066	98,523	288,352
Less: earnings from discontinued operations, net of tax									(12)	570	(39)
Net earnings									158,054	99,093	288,313
Net loss attributable to noncontrolling interests									6,098	5,643	2,059
Net earnings attributable to IAC shareholders									164,152	104,736	290,372
Comprehensive income attributable to IAC shareholders									$ 98,323	$ 33,229	$ 301,073