INVESTMENTS (Details) - USD ($)			3 Months Ended		6 Months Ended
	May. 26, 2015	Aug. 07, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Investments
Weighted maturity of investments					1 year 10 months
Marketable Securities, Realized Gain (Loss)			$ 1,600,000	$ 0	$ 3,400,000	$ 0
Ctrip.com International, Ltd. [Member]
Investments
Debt Investment, Term	5 years	5 years
Period over which Ctrip ADSs can be acquired	12 months	12 months
Maximum Ownership Percentage in Ctrip	15.00%	10.00%
Short-term Investments [Member]
Investments
Cost			1,299,361,000		1,299,361,000		$ 1,142,881,000
Gross Unrealized Gains			149,000		149,000		39,000
Gross Unrealized Losses			(383,000)		(383,000)		(738,000)
Fair Value			1,299,127,000		1,299,127,000		1,142,182,000
Short-term Investments [Member] | Foreign government securities
Investments
Cost			199,505,000		199,505,000		52,524,000
Gross Unrealized Gains			11,000		11,000		0
Gross Unrealized Losses			(55,000)		(55,000)		(34,000)
Fair Value			199,461,000		199,461,000		52,490,000
Short-term Investments [Member] | U.S. government securities
Investments
Cost			587,802,000		587,802,000		364,276,000
Gross Unrealized Gains			75,000		75,000		24,000
Gross Unrealized Losses			(14,000)		(14,000)		(34,000)
Fair Value			587,863,000		587,863,000		364,266,000
Short-term Investments [Member] | Corporate debt securities
Investments
Cost			512,054,000		512,054,000		582,160,000
Gross Unrealized Gains			63,000		63,000		15,000
Gross Unrealized Losses			(314,000)		(314,000)		(652,000)
Fair Value			511,803,000		511,803,000		581,523,000
Short-term Investments [Member] | Commercial paper
Investments
Cost							39,092,000
Gross Unrealized Gains							0
Gross Unrealized Losses							0
Fair Value							39,092,000
Short-term Investments [Member] | U.S. government agency securities
Investments
Cost							104,829,000
Gross Unrealized Gains							0
Gross Unrealized Losses							(18,000)
Fair Value							104,811,000
Long-term Investments [Member]
Investments
Cost			6,274,829,000		6,274,829,000		3,920,019,000
Gross Unrealized Gains			130,175,000		130,175,000		2,476,000
Gross Unrealized Losses			(9,536,000)		(9,536,000)		(166,842,000)
Fair Value			6,395,468,000		6,395,468,000		3,755,653,000
Long-term Investments [Member] | Foreign government securities
Investments
Cost			428,402,000		428,402,000		12,707,000
Gross Unrealized Gains			69,000		69,000		0
Gross Unrealized Losses			(960,000)		(960,000)		(36,000)
Fair Value			427,511,000		427,511,000		12,671,000
Long-term Investments [Member] | U.S. government securities
Investments
Cost			733,461,000		733,461,000		557,130,000
Gross Unrealized Gains			2,108,000		2,108,000		80,000
Gross Unrealized Losses			(409,000)		(409,000)		(762,000)
Fair Value			735,160,000		735,160,000		556,448,000
Long-term Investments [Member] | Corporate debt securities
Investments
Cost			3,937,924,000		3,937,924,000		2,332,030,000
Gross Unrealized Gains			4,295,000		4,295,000		2,299,000
Gross Unrealized Losses			(8,167,000)		(8,167,000)		(5,296,000)
Fair Value			3,934,052,000		3,934,052,000		2,329,033,000
Long-term Investments [Member] | U.S. government agency securities
Investments
Cost			2,015,000		2,015,000		95,108,000
Gross Unrealized Gains			3,000		3,000		97,000
Gross Unrealized Losses			0		0		(111,000)
Fair Value			2,018,000		2,018,000		95,094,000
Long-term Investments [Member] | U.S. municipal securities
Investments
Cost			1,097,000		1,097,000		1,114,000
Gross Unrealized Gains			7,000		7,000		0
Gross Unrealized Losses			0		0		(12,000)
Fair Value			1,104,000		1,104,000		1,102,000
Long-term Investments [Member] | Ctrip convertible debt securities | Ctrip.com International, Ltd. [Member]
Investments
Cost	$ 250,000,000	$ 500,000,000	750,000,000		750,000,000		500,000,000
Gross Unrealized Gains			10,399,000		10,399,000		0
Gross Unrealized Losses			0		0		(74,039,000)
Fair Value			760,399,000		760,399,000		425,961,000
Long-term Investments [Member] | Ctrip equity securities | Ctrip.com International, Ltd. [Member]
Investments
Cost			421,930,000		421,930,000		421,930,000
Gross Unrealized Gains			113,294,000		113,294,000		0
Gross Unrealized Losses			0		0		(86,586,000)
Fair Value			$ 535,224,000		$ 535,224,000		$ 335,344,000