Cash, Cash Equivalents and Short-term and Long-term Investments - Schedule of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities
Cash and cash equivalents, amortized cost		$ 144,064
Gross Unrealized Losses		(12)
Cash and cash equivalents due in 90 days or less	$ 237,677	144,052	$ 100,150
Available-for-sale securities:
Amortized Cost	215,872	147,714
Gross Unrealized Gains	325	0
Gross Unrealized Losses	(28)	(454)
Estimated Fair Value	216,169	147,260
Total cash, cash equivalents and available for sale securities
Amortized Cost	453,549	291,778
Gross Unrealized Gains	325	0
Gross Unrealized Losses	(28)	(466)
Estimated Fair Value	453,846	291,312
Corporate Obligations
Available-for-sale securities:
Amortized Cost	124,676	73,671
Gross Unrealized Gains	219	0
Gross Unrealized Losses	(15)	(267)
Estimated Fair Value	124,880	73,404
US Treasury Securities
Available-for-sale securities:
Amortized Cost	78,230	45,346
Gross Unrealized Gains	98	0
Gross Unrealized Losses	(1)	(79)
Estimated Fair Value	78,327	45,267
Certificates of Deposit
Available-for-sale securities:
Amortized Cost	490	1,715
Gross Unrealized Gains	3	0
Gross Unrealized Losses	0	0
Estimated Fair Value	493	1,715
Asset-backed Securities
Available-for-sale securities:
Amortized Cost	12,476	26,982
Gross Unrealized Gains	5	0
Gross Unrealized Losses	(12)	(108)
Estimated Fair Value	$ 12,469	$ 26,874

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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