QUARTERLY RESULTS (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 12 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 30, 2016 |
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Quarterly Financial Information Disclosure [Abstract] | ||||||||||||
| Revenue | $ 811,162 | $ 764,102 | $ 745,439 | $ 819,179 | $ 848,728 | $ 838,561 | $ 771,132 | $ 772,512 | $ 3,139,882 | $ 3,230,933 | $ 3,109,547 | |
| Cost of revenue | 212,468 | 179,131 | 170,397 | 193,734 | 214,084 | 199,377 | 177,963 | 186,737 | 755,730 | 778,161 | 860,204 | |
| Operating income (loss) | 112,820 | 85,584 | (252,446) | 21,417 | (5,430) | 87,130 | 62,769 | 35,119 | (32,625) | 179,588 | 378,727 | |
| Earnings (loss) from continuing operations | 113,928 | 52,340 | (190,542) | 7,934 | (31,417) | 65,026 | 57,885 | 21,863 | (16,340) | 113,357 | 234,557 | |
| Net earnings (loss) | 114,117 | 52,340 | (190,542) | 7,934 | (31,389) | 65,043 | 57,732 | 21,988 | (16,151) | 113,374 | 409,230 | |
| Net earnings (loss) attributable to IAC shareholders | $ 102,051 | $ 43,162 | $ (194,775) | $ 8,282 | $ (31,849) | $ 65,611 | $ 59,305 | $ 26,405 | $ (41,280) | $ 119,472 | $ 414,873 | |
| Per share information attributable to IAC shareholders: | ||||||||||||
| Basic earnings (loss) per share from continuing operations (in usd per share) | $ 1.29 | $ 0.54 | $ (2.45) | $ 0.10 | $ (0.38) | $ 0.79 | $ 0.72 | $ 0.31 | $ (0.52) | $ 1.44 | $ 2.88 | |
| Diluted earnings (loss) per share from continuing operations (in usd per share) | 1.18 | 0.49 | (2.45) | 0.09 | (0.38) | 0.74 | 0.68 | 0.30 | (0.52) | 1.33 | 2.71 | |
| Basic earnings (loss) per share (in usd per share) | 1.29 | 0.54 | (2.45) | 0.10 | (0.38) | 0.79 | 0.72 | 0.32 | (0.52) | 1.44 | 4.98 | |
| Diluted earnings (loss) per share (in usd per share) | $ 1.18 | $ 0.49 | $ (2.45) | $ 0.09 | $ (0.38) | $ 0.74 | $ 0.68 | $ 0.30 | $ (0.52) | $ 1.33 | $ 4.68 | |
| Additional consolidated financial statement details | ||||||||||||
| Goodwill impairment charges, net of tax | $ 183,500 | $ 14,100 | ||||||||||
| Write-down of indefinite-lived intangible assets, net of tax | $ 7,200 | $ 55,300 | ||||||||||
| Disposal Group, Disposed of by Sale, Not Discontinued Operations | PriceRunner | ||||||||||||
| Additional consolidated financial statement details | ||||||||||||
| Gain on sale of business | $ 11,900 | |||||||||||
| Disposal Group, Disposed of by Sale, Not Discontinued Operations | ShoeBuy | ||||||||||||
| Additional consolidated financial statement details | ||||||||||||
| Gain on sale of business | $ 37,500 | $ 37,500 | ||||||||||