GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION (Details3) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	$ 324,330	$ 323,607
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	(39,457)	(377,123)
Capital expenditures	(64,114)	(32,363)
Proceeds from maturities and sales of marketable debt securities	12,502	79,353
Purchases of marketable debt securities	0	(47,902)
Proceeds from sales of long-term investments	42,286	12,744
Purchases of long-term investments	(26,605)	(10,031)
Other, net	8,904	(12,264)
Net cash used in investing activities attributable to continuing operations	(66,484)	(387,586)
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	(168,376)	(434,041)
Issuance of common stock, net of withholding taxes	6,456	320,070
Dividends	(58,882)	(43,695)
Excess tax benefits from stock-based awards	26,430	23,486
Payments to Noncontrolling Interests	55,561	4,891
Principal payments on long-term debt	(15,844)	0
Other, net	(3,386)	195
Net cash used in financing activities attributable to continuing operations	(269,163)	(138,876)
Total cash used in continuing operations	(11,317)	(202,855)
Total cash provided by (used in) discontinued operations	2,257	(1,866)
Effect of exchange rate changes on cash and cash equivalents	735	2,347
Net decrease in cash and cash equivalents	(8,325)	(202,374)
Cash and cash equivalents at beginning of period	749,977	704,153
Cash and cash equivalents at end of period	741,652	501,779
IAC
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	(55,102)	(25,409)
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	0	0
Capital expenditures	(742)	(805)
Proceeds from maturities and sales of marketable debt securities	12,502	79,353
Purchases of marketable debt securities		(47,902)
Proceeds from sales of long-term investments	41,976	12,744
Purchases of long-term investments	(17,362)	(2,588)
Other, net	0	(350)
Net cash used in investing activities attributable to continuing operations	36,374	40,452
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	(168,376)	(434,041)
Issuance of common stock, net of withholding taxes	6,456	320,070
Dividends	(58,882)	(43,695)
Excess tax benefits from stock-based awards	26,430	18,594
Payments to Noncontrolling Interests	0	(1,937)
Principal payments on long-term debt	(15,844)
Intercompany	178,663	(153,633)
Other, net	(951)	0
Net cash used in financing activities attributable to continuing operations	(32,504)	(294,642)
Total cash used in continuing operations	(51,232)	(279,599)
Total cash provided by (used in) discontinued operations	2,254	2,576
Effect of exchange rate changes on cash and cash equivalents	0	0
Net decrease in cash and cash equivalents	(48,978)	(277,023)
Cash and cash equivalents at beginning of period	501,075	545,222
Cash and cash equivalents at end of period	452,097	268,199
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	392,407	337,883
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	(6,084)	(341,906)
Capital expenditures	(52,098)	(20,295)
Proceeds from maturities and sales of marketable debt securities	0	0
Purchases of marketable debt securities		0
Proceeds from sales of long-term investments	0	0
Purchases of long-term investments	0	(724)
Other, net	(1,717)	117
Net cash used in investing activities attributable to continuing operations	(59,899)	(362,808)
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	0	0
Issuance of common stock, net of withholding taxes	0	0
Dividends	0	0
Excess tax benefits from stock-based awards	0	4,892
Payments to Noncontrolling Interests	0	0
Principal payments on long-term debt	0
Intercompany	(331,295)	20,052
Other, net	(1,225)	0
Net cash used in financing activities attributable to continuing operations	(332,520)	24,944
Total cash used in continuing operations	(12)	19
Total cash provided by (used in) discontinued operations	0	0
Effect of exchange rate changes on cash and cash equivalents	12	(19)
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	(12,975)	11,133
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	(33,373)	(35,217)
Capital expenditures	(11,274)	(11,263)
Proceeds from maturities and sales of marketable debt securities	0	0
Purchases of marketable debt securities		0
Proceeds from sales of long-term investments	310	0
Purchases of long-term investments	(9,243)	(6,719)
Other, net	10,621	(12,031)
Net cash used in investing activities attributable to continuing operations	(42,959)	(65,230)
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	0	0
Issuance of common stock, net of withholding taxes	0	0
Dividends	0	0
Excess tax benefits from stock-based awards	0	0
Payments to Noncontrolling Interests	(55,561)	(2,954)
Principal payments on long-term debt	0
Intercompany	152,632	133,581
Other, net	(1,210)	195
Net cash used in financing activities attributable to continuing operations	95,861	130,822
Total cash used in continuing operations	39,927	76,725
Total cash provided by (used in) discontinued operations	3	(4,442)
Effect of exchange rate changes on cash and cash equivalents	723	2,366
Net decrease in cash and cash equivalents	40,653	74,649
Cash and cash equivalents at beginning of period	248,902	158,931
Cash and cash equivalents at end of period	289,555	233,580
Total Eliminations
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	0	0
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	0	0
Capital expenditures	0	0
Proceeds from maturities and sales of marketable debt securities	0	0
Purchases of marketable debt securities		0
Proceeds from sales of long-term investments	0	0
Purchases of long-term investments	0	0
Other, net	0	0
Net cash used in investing activities attributable to continuing operations	0	0
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	0	0
Issuance of common stock, net of withholding taxes	0	0
Dividends	0	0
Excess tax benefits from stock-based awards	0	0
Payments to Noncontrolling Interests	0	0
Principal payments on long-term debt	0
Intercompany	0	0
Other, net	0	0
Net cash used in financing activities attributable to continuing operations	0	0
Total cash used in continuing operations	0	0
Total cash provided by (used in) discontinued operations	0	0
Effect of exchange rate changes on cash and cash equivalents	0	0
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
IAC Consolidated
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	324,330	323,607
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	(39,457)	(377,123)
Capital expenditures	(64,114)	(32,363)
Proceeds from maturities and sales of marketable debt securities	12,502	79,353
Purchases of marketable debt securities		(47,902)
Proceeds from sales of long-term investments	42,286	12,744
Purchases of long-term investments	(26,605)	(10,031)
Other, net	8,904	(12,264)
Net cash used in investing activities attributable to continuing operations	(66,484)	(387,586)
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	(168,376)	(434,041)
Issuance of common stock, net of withholding taxes	6,456	320,070
Dividends	(58,882)	(43,695)
Excess tax benefits from stock-based awards	26,430	23,486
Payments to Noncontrolling Interests	(55,561)	(4,891)
Principal payments on long-term debt	(15,844)
Intercompany	0	0
Other, net	(3,386)	195
Net cash used in financing activities attributable to continuing operations	(269,163)	(138,876)
Total cash used in continuing operations	(11,317)	(202,855)
Total cash provided by (used in) discontinued operations	2,257	(1,866)
Effect of exchange rate changes on cash and cash equivalents	735	2,347
Net decrease in cash and cash equivalents	(8,325)	(202,374)
Cash and cash equivalents at beginning of period	749,977	704,153
Cash and cash equivalents at end of period	$ 741,652	$ 501,779