Balance Sheet Components (Fair Value of Available-For-Sale Investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Money Market Funds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 93,977	$ 60,295
Estimated Fair Value	93,977	60,295
Commercial Paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,292	39,577
Estimated Fair Value	13,292	39,577
Corporate Bonds/Notes [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,905	7,970
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	7,904	7,969
U.S. Government Securitie [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20,294	38,430
Gross Unrealized Gains	7	42
Gross Unrealized Losses		(2)
Estimated Fair Value	20,301	38,470
Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	135,468	146,272
Gross Unrealized Gains	7	42
Gross Unrealized Losses	(1)	(3)
Estimated Fair Value	135,474	146,311
Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	93,977	68,295
Short-Term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	41,497	78,016
Long-Term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 135,474	$ 146,311

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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