Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Securities, Available-for-sale [Line Items]
Cash	$ 37,190	$ 135,092
Time deposits	3,810	3,682
Money market funds	120,832	116,068
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	1,117,175	2,169,197
Total	1,279,007	2,424,039
Included in Cash and cash equivalents	357,415	465,851
Included in Other assets (Restricted cash)	9,338	9,288
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	366,753	475,139	$ 241,581	$ 240,628
Included in Marketable securities	$ 912,254	$ 1,948,900

Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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