EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Weighted Average Number of Shares Issued, Basic									83,292	83,480	86,247
Numerator: Basic
Earnings from continuing operations	$ 67,986	$ 150,261	$ (17,995)	$ 34,305	$ 78,829	$ 91,721	$ 58,540	$ 52,709	$ 234,557	$ 281,799	$ 169,847
Net loss (earnings) attributable to noncontrolling interests									5,643	2,059	(1,530)
Earnings (loss) from continuing operations attributable to IAC shareholders									240,200	283,858	168,317
Less: earnings (loss) from discontinued operations, net of tax	625	175,730	(868)	(814)	24	3,914	(1,068)	(944)	174,673	1,926	(9,051)
Net earnings attributable to IAC shareholders	70,172	326,812	(17,996)	35,885	76,917	96,940	58,290	53,637	414,873	285,784	159,266
Numerator: Diluted
Earnings (loss) from continuing operations	67,986	150,261	(17,995)	34,305	78,829	91,721	58,540	52,709	234,557	281,799	169,847
Net loss (earnings) attributable to noncontrolling interests									5,643	2,059	(1,530)
Earnings (loss) from continuing operations attributable to IAC shareholders									240,200	283,858	168,317
Less: earnings (loss) from discontinued operations, net of tax	625	175,730	(868)	(814)	24	3,914	(1,068)	(944)	174,673	1,926	(9,051)
Net earnings (loss) attributable to IAC shareholders									$ 414,873	$ 285,784	$ 159,266
Denominator: Basic
Weighted average basic shares outstanding									83,292	83,480	86,247
Denominator: Diluted
Weighted average basic shares outstanding									83,292	83,480	86,247
Dilutive securities including stock options, warrants and RSUs (in shares)									5,266	3,262	6,842
Denominator for earnings per share-weighted average shares (in shares)									88,558	86,742	93,089
Earnings per share attributable to IAC shareholders: Basic
Earnings per share from continuing operations (in dollars per share)	$ 0.83	$ 1.81	$ (0.21)	$ 0.44	$ 0.93	$ 1.12	$ 0.71	$ 0.65	$ 2.88	$ 3.40	$ 1.95
Discontinued operations, net of tax (in dollars per share)									$ 2.10	$ 0.02	$ (0.10)
Earnings per share (in dollars per share)	$ 0.84	$ 3.91	$ (0.22)	$ 0.44	$ 0.93	$ 1.17	$ 0.70	$ 0.64	$ 4.98	$ 3.42	$ 1.85
Earnings (loss) per share attributable to IAC shareholders: Diluted
Earnings per share from continuing operations (in dollars per share)	$ 0.78	$ 1.70	$ (0.21)	$ 0.42	$ 0.88	$ 1.08	$ 0.69	$ 0.62	$ 2.71	$ 3.27	$ 1.81
Discontinued operations, net of tax (in dollars per share)									$ 1.97	$ 0.02	$ (0.10)
Earnings per share (in dollars per share)	$ 0.78	$ 3.68	$ (0.22)	$ 0.41	$ 0.88	$ 1.13	$ 0.67	$ 0.61	$ 4.68	$ 3.29	$ 1.71