Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities - Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair value of marketable securities
Total marketable investment securities	$ 132,593	$ 390
Fair value measurements on recurring basis
Fair value of marketable securities
Cash equivalents (including restricted)	1,278,971	60,677
Total marketable investment securities	132,593	390
Fair value measurements on recurring basis \| U.S. Treasury and agency securities
Fair value of marketable securities
Debt securities	22,476	390
Fair value measurements on recurring basis \| Commercial paper
Fair value of marketable securities
Debt securities	101,959
Fair value measurements on recurring basis \| Corporate securities
Fair value of marketable securities
Debt securities	8,068
Fair value measurements on recurring basis \| Other
Fair value of marketable securities
Debt securities	90
Fair value measurements on recurring basis \| Level 1
Fair value of marketable securities
Cash equivalents (including restricted)	172,025	60,677
Total marketable investment securities	22,476	390
Fair value measurements on recurring basis \| Level 1 \| U.S. Treasury and agency securities
Fair value of marketable securities
Debt securities	22,476	$ 390
Fair value measurements on recurring basis \| Level 2
Fair value of marketable securities
Cash equivalents (including restricted)	1,106,946
Total marketable investment securities	110,117
Fair value measurements on recurring basis \| Level 2 \| Commercial paper
Fair value of marketable securities
Debt securities	101,959
Fair value measurements on recurring basis \| Level 2 \| Corporate securities
Fair value of marketable securities
Debt securities	8,068
Fair value measurements on recurring basis \| Level 2 \| Other
Fair value of marketable securities
Debt securities	$ 90

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
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
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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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