GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION (Details3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	$ 92,362	$ 59,050
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	(29,194)	(10,267)
Capital expenditures	(33,638)	(9,633)
Proceeds from maturities and sales of marketable debt securities	12,500	18,343
Purchases of marketable debt securities	0	(10,012)
Proceeds from sales of long-term investments	214	8,058
Purchases of long-term investments	(975)	(470)
Other, net	(1,051)	(8,253)
Net cash used in investing activities attributable to continuing operations	(52,144)	(12,234)
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	(88,605)	(222,863)
Issuance of common stock, net of withholding taxes	552	99,212
Dividends	(21,429)	(10,573)
Excess tax benefits from stock-based awards	12,530	6,477
Principal payments on long-term debt	(15,844)
Other, net	(1,101)	22
Net cash used in financing activities attributable to continuing operations	(113,897)	(127,725)
Total cash used in continuing operations	(73,679)	(80,909)
Total cash provided by (used in) discontinued operations	2,425	(368)
Effect of exchange rate changes on cash and cash equivalents	(4,966)	1,220
Net decrease in cash and cash equivalents	(76,220)	(80,057)
Cash and cash equivalents at beginning of period	749,977	704,153
Cash and cash equivalents at end of period	673,757	624,096
IAC Consolidated
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	92,362	59,050
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	(29,194)	(10,267)
Capital expenditures	(33,638)	(9,633)
Proceeds from maturities and sales of marketable debt securities	12,500	18,343
Purchases of marketable debt securities		(10,012)
Proceeds from sales of long-term investments	214	8,058
Purchases of long-term investments	(975)	(470)
Other, net	(1,051)	(8,253)
Net cash used in investing activities attributable to continuing operations	(52,144)	(12,234)
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	(88,605)	(222,863)
Issuance of common stock, net of withholding taxes	552	99,212
Dividends	(21,429)	(10,573)
Excess tax benefits from stock-based awards	12,530	6,477
Principal payments on long-term debt	(15,844)
Intercompany	0	0
Other, net	(1,101)	22
Net cash used in financing activities attributable to continuing operations	(113,897)	(127,725)
Total cash used in continuing operations	(73,679)	(80,909)
Total cash provided by (used in) discontinued operations	2,425	(368)
Effect of exchange rate changes on cash and cash equivalents	(4,966)	1,220
Net decrease in cash and cash equivalents	(76,220)	(80,057)
Cash and cash equivalents at beginning of period	749,977	704,153
Cash and cash equivalents at end of period	673,757	624,096
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
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
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	(12,099)	(3,937)
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	(23,134)	0
Capital expenditures	(28,501)	(3,420)
Proceeds from maturities and sales of marketable debt securities	0	0
Purchases of marketable debt securities		0
Proceeds from sales of long-term investments	214	0
Purchases of long-term investments	(975)	(450)
Other, net	(996)	(7,604)
Net cash used in investing activities attributable to continuing operations	(53,392)	(11,474)
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
Principal payments on long-term debt	0
Intercompany	65,130	32,068
Other, net	(145)	22
Net cash used in financing activities attributable to continuing operations	64,985	32,090
Total cash used in continuing operations	(506)	16,679
Total cash provided by (used in) discontinued operations	(1)	(35)
Effect of exchange rate changes on cash and cash equivalents	(4,994)	1,228
Net decrease in cash and cash equivalents	(5,501)	17,872
Cash and cash equivalents at beginning of period	248,902	158,931
Cash and cash equivalents at end of period	243,401	176,803
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	105,567	82,531
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	(6,060)	(10,267)
Capital expenditures	(5,059)	(6,182)
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	(20)
Other, net	0	(299)
Net cash used in investing activities attributable to continuing operations	(11,119)	(16,768)
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
Principal payments on long-term debt	0
Intercompany	(94,447)	(65,755)
Other, net	(29)	0
Net cash used in financing activities attributable to continuing operations	(94,476)	(65,755)
Total cash used in continuing operations	(28)	8
Total cash provided by (used in) discontinued operations	0	0
Effect of exchange rate changes on cash and cash equivalents	28	(8)
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
Condensed Financial Statements, Captions [Line Items]
Net cash (used in) provided by operating activities attributable to continuing operations	(1,106)	(19,544)
Cash flows from investing activities attributable to continuing operations:
Acquisitions, net of cash acquired	0	0
Capital expenditures	(78)	(31)
Proceeds from maturities and sales of marketable debt securities	12,500	18,343
Purchases of marketable debt securities		(10,012)
Proceeds from sales of long-term investments	0	8,058
Purchases of long-term investments	0	0
Other, net	(55)	(350)
Net cash used in investing activities attributable to continuing operations	12,367	16,008
Cash flows from financing activities attributable to continuing operations:
Purchase of treasury stock	(88,605)	(222,863)
Issuance of common stock, net of withholding taxes	552	99,212
Dividends	(21,429)	(10,573)
Excess tax benefits from stock-based awards	12,530	6,477
Principal payments on long-term debt	(15,844)
Intercompany	29,317	33,687
Other, net	(927)	0
Net cash used in financing activities attributable to continuing operations	(84,406)	(94,060)
Total cash used in continuing operations	(73,145)	(97,596)
Total cash provided by (used in) discontinued operations	2,426	(333)
Effect of exchange rate changes on cash and cash equivalents	0	0
Net decrease in cash and cash equivalents	(70,719)	(97,929)
Cash and cash equivalents at beginning of period	501,075	545,222
Cash and cash equivalents at end of period	$ 430,356	$ 447,293