Fair Value Measurements and Available for Sale Investments - Available-for-sale Investments (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 164,902
Gross Unrealized Gains	481
Gross Unrealized Losses	(14)
Total Fair Value	165,369
Short-term investments	129,192	$ 203,210
Long-term investments	36,177	$ 54,305
Agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,790
Gross Unrealized Gains	16
Gross Unrealized Losses	(1)
Total Fair Value	15,805
Short-term investments	$ 800
Investments outstanding, maturity date range (in years)	1 year
Long-term investments	$ 15,000
Agency securities \| Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
Agency securities \| Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 3,696
Gross Unrealized Gains	17
Gross Unrealized Losses	0
Total Fair Value	3,713
Short-term investments	$ 3,000
Investments outstanding, maturity date range (in years)	1 year
Long-term investments	$ 700
Certificates of deposit \| Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
Certificates of deposit \| Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years
Commercial and corporate obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 38,590
Gross Unrealized Gains	105
Gross Unrealized Losses	(3)
Total Fair Value	$ 38,692
Commercial and corporate obligations \| Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 106,826
Gross Unrealized Gains	343
Gross Unrealized Losses	(10)
Total Fair Value	107,159
Short-term investments	86,700
Long-term investments	$ 20,400
U.S. Treasury securities \| Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
U.S. Treasury securities \| Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years

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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).

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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), classified as current.

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