Marketable Securities and Fair Value Measurements - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair value measurements
Amortized Cost	$ 559,910	$ 121,005
Gross Unrealized Gains	112
Gross Unrealized Losses	(80)	(201)
Estimated Fair Value	559,942	120,804
Short-term investments
Fair value measurements
Amortized Cost	404,294	114,402
Gross Unrealized Gains	20
Gross Unrealized Losses	(62)	(124)
Estimated Fair Value	404,252	114,278
Long-term investments
Fair value measurements
Amortized Cost	155,616	6,603
Gross Unrealized Gains	92
Gross Unrealized Losses	(18)	(77)
Estimated Fair Value	$ 155,690	$ 6,526

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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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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