COMMITMENTS AND CONTINGENCIES (Details) (USD $)	12 Months Ended		3 Months Ended			12 Months Ended		43 Months Ended		1 Months Ended					3 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Litigation Related to Hotel Occupany and Other Taxes [Member] Cases	Dec. 31, 2012 Litigation Related to Anti-trust Violations [Member] Cases	Sep. 30, 2012 Litigation Related to Anti-trust Violations [Member] Cases	Dec. 31, 2012 Minimum [Member] Litigation Related to Hotel Occupany and Other Taxes [Member] GovernmentalUnit	Dec. 31, 2012 US Merchant Hotel Business [Member] Litigation Related to Hotel Occupany and Other Taxes [Member]	Dec. 31, 2011 US Merchant Hotel Business [Member] Litigation Related to Hotel Occupany and Other Taxes [Member]	Jan. 31, 2013 State of California [Member] Litigation Related to Hotel Occupany and Other Taxes [Member] Cases	Dec. 31, 2012 State of California [Member] Minimum [Member] Litigation Related to Hotel Occupany and Other Taxes [Member] GovernmentalUnit	Jan. 31, 2013 City of San Francisco [Member] Litigation Related to Hotel Occupany and Other Taxes [Member]	Jul. 31, 2009 City of San Francisco [Member] Litigation Related to Hotel Occupany and Other Taxes [Member]	Dec. 31, 2012 Cities in Arizona Other then Pheonix [Member] Litigation Related to Hotel Occupany and Other Taxes [Member]	Dec. 31, 2012 UTAH [Member] Litigation Related to Hotel Occupany and Other Taxes [Member]	Sep. 30, 2012 COLORADO [Member] Litigation Related to Hotel Occupany and Other Taxes [Member] GovernmentalUnit	Dec. 31, 2012 HAWAII [Member] Litigation Related to Hotel Occupany and Other Taxes [Member]	Sep. 30, 2012 District of Columbia [Member] Litigation Related to Hotel Occupany and Other Taxes [Member]	Jul. 31, 2012 Booking.com B.V. [Member] Minimum [Member]	Jul. 31, 2012 Booking.com B.V. [Member] Maximum [Member]
Hotel Occupany and Other Taxes
Approximate number of lawsuits brought by or against states, cities and counties over issues involving the payment of hotel occupancy and other taxes		40
Number of consumer class actions		1
Minimum number of states which have initiated audit proceedings					12
Minimum number of municipalities and counties which have initiated audit proceedings					70				40
Loss Contingency Related To Hotel Occupancy And Other Taxes Pay To Play (In dollars)								2
Assessed taxes including interest and penalties (in dollars)										$ 2,700,000	$ 3,400,000				$ 16,500,000	$ 4,800,000
Estimated Gross Profit, Since Inception (In dollars)						1,600,000,000
Aggregate tax rates, low end of the range (as a percent)						6.00%
Aggregate tax rates, high end of the range (as a percent)						18.00%
Reserve for the potential resolution of issues related to hotel occupancy and other taxes (in dollars)						56,000,000	33,000,000
Number of currently pending lawsuits that commenced in period		6
Audit notices and administrative procedures, number of cities												12	5
Number of appeals remaining unresolved														15
OFT Inquiry [Abstract]
UK OFT Inquiry Potential Infringement Decision																	0	50,000,000
Loss Contingency Complaints Filed Alleging Antitrust Violations [Abstract]
Loss Contingency Complaint Filed Alleging Antitrust Violations				1
Loss Continency Other Complaints Alleging Antitrust Violations			31
Contingency Consolidation Of Complaints Alleging Antitrust Violations			30
Employment Contracts [Abstract]
Maximum cash severance payments provided for in the employment agreements	$ 25,000,000
Extension period for health and insurance benefits after termination, high end of range (in years)	3 years