Balance Sheet Components - Fair Value of Available-For-Sale Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 146,272	$ 104,093
Gross Unrealized Gains	42	9
Gross Unrealized Losses	(3)	(7)
Estimated Fair Value	146,311	104,095
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	60,295	34,363
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	60,295	34,363
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	39,577	9,919
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	39,577	9,919
Corporate bonds/notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,970	10,180
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(4)
Estimated Fair Value	7,969	10,176
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	38,430	44,450
Gross Unrealized Gains	42	9
Gross Unrealized Losses	(2)	(3)
Estimated Fair Value	38,470	44,456
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		5,181
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Value		5,181
Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	68,295	34,363
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 78,016	51,508
Long-term investments
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value		$ 18,224

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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