Marketable Securities and Fair Value Measurements - Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investments, All Other Investments [Abstract]
One year or less	$ 318,202	$ 98,460
One year through two years	0	9,112
Marketable Securities	$ 318,202	$ 107,572

No definition available.

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Amount of investment in marketable security.

+ References

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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Amount of investment in marketable security, classified as current.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Amount of investment in marketable security, classified as noncurrent.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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