FAIR VALUE MEASUREMENTS Cost method investments and derivatives (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Sep. 12, 2016	Dec. 11, 2015	May 26, 2015	Aug. 07, 2014
Fair Value Disclosures [Abstract]
Cost Method Investments	$ 8,200,000		$ 8,200,000		$ 7,600,000
Derivatives Not Designated as Hedging Instruments
Foreign currency gains (losses), net of derivative activity	(7,600,000)	$ (3,600,000)	(18,700,000)	$ (10,600,000)
Foreign Currency Contracts, Translation Risk
Derivatives Not Designated as Hedging Instruments
Foreign currency gains (losses) recorded in Foreign currency transactions and other	(1,100,000)	0	(1,300,000)	0
Foreign currency derivative instruments not designated as hedging instruments at fair value, net	0		0		0
Foreign Currency Contracts, Transaction Risk
Derivatives Not Designated as Hedging Instruments
Foreign currency gains (losses) recorded in Foreign currency transactions and other	10,700,000	$ 5,000,000	38,300,000	21,000,000
Foreign currency derivative instruments not designated as hedging instruments at fair value, net	(1,600,000)		(1,600,000)		(300,000)
Foreign currency derivative assets recorded in Prepaid expenses and other current assets	100,000		100,000		700,000
Foreign currency derivative liabilities recorded in Accrued expenses and other current liabilities	1,700,000		1,700,000		1,000,000
Foreign Currency Contracts
Derivatives Not Designated as Hedging Instruments
Net cash inflow from settlement of derivative contracts included in operating activities			38,200,000	$ 34,300,000
Long-term Investments
Derivatives Not Designated as Hedging Instruments
Available-for-sale securities, amortized cost basis	10,401,379,000		10,401,379,000		9,407,136,000
Ctrip.com International, Ltd.
Derivatives Not Designated as Hedging Instruments
Embedded derivative, gain (loss) on embedded Derivative	(300,000)		1,700,000
Ctrip.com International, Ltd. | Ctrip convertible debt securities | Long-term Investments
Derivatives Not Designated as Hedging Instruments
Available-for-sale securities, amortized cost basis	1,275,000,000		1,275,000,000		1,275,000,000	$ 25,000,000	$ 500,000,000	$ 250,000,000	$ 500,000,000
Embedded derivative, fair value of embedded derivative	$ 3,500,000		$ 3,500,000		$ 1,800,000