Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities - Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair value of marketable securities
Debt securities	$ 446,075	$ 390
Total marketable investment securities	446,075	390
U.S. Treasury and agency securities
Fair value of marketable securities
Debt securities	130,592	390
Commercial paper
Fair value of marketable securities
Debt securities	287,124
Corporate securities
Fair value of marketable securities
Debt securities	28,212
Other
Fair value of marketable securities
Debt securities	147
Fair value measurements on recurring basis
Fair value of marketable securities
Cash equivalents (including restricted)	867,906	60,677
Total marketable investment securities	446,075	390
Fair value measurements on recurring basis \| U.S. Treasury and agency securities
Fair value of marketable securities
Debt securities	130,592	390
Fair value measurements on recurring basis \| Commercial paper
Fair value of marketable securities
Debt securities	287,124
Fair value measurements on recurring basis \| Corporate securities
Fair value of marketable securities
Debt securities	28,212
Fair value measurements on recurring basis \| Other
Fair value of marketable securities
Debt securities	147
Fair value measurements on recurring basis \| Level 1
Fair value of marketable securities
Cash equivalents (including restricted)	495,119	60,677
Total marketable investment securities	130,592	390
Fair value measurements on recurring basis \| Level 1 \| U.S. Treasury and agency securities
Fair value of marketable securities
Debt securities	130,592	$ 390
Fair value measurements on recurring basis \| Level 2
Fair value of marketable securities
Cash equivalents (including restricted)	372,787
Total marketable investment securities	315,483
Fair value measurements on recurring basis \| Level 2 \| Commercial paper
Fair value of marketable securities
Debt securities	287,124
Fair value measurements on recurring basis \| Level 2 \| Corporate securities
Fair value of marketable securities
Debt securities	28,212
Fair value measurements on recurring basis \| Level 2 \| Other
Fair value of marketable securities
Debt securities	$ 147

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
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-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investment in marketable security.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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