CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other comprehensive income (loss), net of tax
Net income		$ 2,340,765	$ 2,134,987	$ 2,551,360
Foreign currency translation adjustments	[1]	295,547	(93,984)	(114,505)
Net unrealized gain (loss) on marketable securities	[2]	76,119	(285,552)	619,259
Comprehensive income		2,712,431	1,755,451	3,056,114
Tax (benefit) associated with gain (loss) on net investment hedges		(174,584)	34,268	60,418
Tax (benefit) associated with gain (loss) on marketable securities		81,166	15,313	1,551
Domestic Tax Authority
Other comprehensive income (loss), net of tax
Tax (benefit) associated with gain (loss) on marketable securities		63,353
Ctrip.com International, Ltd. | The Netherlands
Other comprehensive income (loss), net of tax
Net unrealized gain (loss) on marketable securities which are non-taxable in the Netherlands		$ 86,019	$ (332,756)	$ 615,848

[1] Foreign currency translation adjustments result from currency fluctuations on the translation of the Company's international non-U.S. Dollar denominated net assets, net of the impact of net investment hedges. Foreign currency translation adjustments were favorable for the year ended December 31, 2017 compared to the year ended December 31, 2016 because the U.S. Dollar weakened against certain currencies in which the Company's net assets are denominated. Foreign currency translation adjustments also include a tax benefit of $174,584 for the year ended December 31, 2017 and tax charges of $34,268 and $60,418 for the years ended December 31, 2016 and 2015, respectively, associated with the Company's Euro-denominated debt, which is designated as a net investment hedge against the impact of currency fluctuations of the Company's Euro-denominated net assets (see Note 12). Prior to the U.S. Tax Cuts and Jobs Act (the "Tax Act"), the remaining balance in foreign currency translation adjustments excluded U.S. federal and state income taxes as a result of the Company's intention to indefinitely reinvest the earnings of its international subsidiaries outside of the United States. In accordance with the Tax Act, generally future repatriation of the Company's international cash will not be subject to a U.S. federal income tax liability as a dividend, but will be subject to U.S. state income taxes and international withholding taxes.

[2] Net of tax charges of $81,166, $15,313 and $1,551 for the years ended December 31, 2017, 2016 and 2015, respectively. For the year ended December 31, 2017, the Company recorded a U.S. deferred tax liability of $63,353 related to net cumulative unrealized gains associated with certain international investments, which will be subject to U.S. federal and state income taxes if the gains are realized. Net unrealized gain (loss) on marketable securities includes net unrealized gains of $86,019 for the year ended December 31, 2017, net unrealized losses of $332,756 for the year ended December 31, 2016, and net unrealized gains of $615,848 for the year ended December 31, 2015, related to the Company's investments in Ctrip.com International Ltd. ("Ctrip"), which are exempt from tax in the Netherlands.