Available-for-Sale Securities and Fair Value Measurements - Schedule of Available-for-Sale Securities (Details) - Estimate of fair value measurement - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 302,247	$ 192,280
Gross Unrealized Gains	270	2
Gross Unrealized Losses	(11)	(72)
Estimated Fair Value	302,506	192,210
Corporate bonds \| Level 2
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	109,780	54,513
Gross Unrealized Gains	136	2
Gross Unrealized Losses	(6)	(46)
Estimated Fair Value	109,910	54,469
Commercial paper \| Level 2
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	41,237	67,906
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	41,237	67,906
Asset-backed securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	57,195	10,970
Gross Unrealized Gains	63	0
Gross Unrealized Losses	(5)	(5)
Estimated Fair Value	57,253	10,965
Repurchase agreements \| Level 2
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	18,000	15,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	18,000	15,000
U.S. treasury securities \| Level 1
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	75,574	39,308
Gross Unrealized Gains	71	0
Gross Unrealized Losses	0	(21)
Estimated Fair Value	75,645	39,287
Money market funds \| Level 1
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	461	4,583
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 461	$ 4,583

Available for sale securities including cash equivalents.

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- Definition

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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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