Investments and Fair Value Measurements - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Marketable securities and fair value measurements
Amortized Cost	$ 265,719	$ 559,910
Gross Unrealized Gains	992	112
Gross Unrealized Losses	(214)	(80)
Estimated Fair Value	266,497	559,942
Short-term Investment securities
Marketable securities and fair value measurements
Amortized Cost	265,719	404,294
Gross Unrealized Gains	992	20
Gross Unrealized Losses	(214)	(62)
Estimated Fair Value	$ 266,497	404,252
Long-term Investment securities
Marketable securities and fair value measurements
Amortized Cost		155,616
Gross Unrealized Gains		92
Gross Unrealized Losses		(18)
Estimated Fair Value		$ 155,690

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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