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Fair Value Measurements and Available for Sale Investments - Available-for-sale Investments (Details) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2021 | Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 64,050 | $ 160,540
Gross Unrealized Gains | 37 | 208
Gross Unrealized Losses | (6) | (5)
Total Fair Value | 64,081 | 160,743
Short-term investments | 58,597 | 143,197
Long-term investments | 5,484 | 17,546
Agency securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 5,003 | 21,169
Gross Unrealized Gains | 0 | 1
Gross Unrealized Losses | (6) | (1)
Total Fair Value | 4,997 | 21,169
Short-term investments | $ 0 | 10,000
Investments outstanding, maturity date range (in years) | 1 year |
Long-term investments | $ 5,000 | $ 11,200
Agency securities | Minimum |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments outstanding, maturity date range (in years) | 1 year | 1 year
Agency securities | Maximum |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments outstanding, maturity date range (in years) | 2 years | 2 years
Certificates of deposit |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 1,589 | $ 2,427
Gross Unrealized Gains | 2 | 9
Gross Unrealized Losses | 0 | 0
Total Fair Value | 1,591 | 2,436
Short-term investments | $ 1,100 | 1,100
Investments outstanding, maturity date range (in years) | 1 year |
Long-term investments | $ 500 | $ 1,300
Certificates of deposit | Minimum |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments outstanding, maturity date range (in years) | 1 year | 1 year
Certificates of deposit | Maximum |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments outstanding, maturity date range (in years) | 2 years | 2 years
Commercial and corporate obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 11,778 | $ 29,414
Gross Unrealized Gains | 1 | 28
Gross Unrealized Losses | 0 | (1)
Total Fair Value | $ 11,779 | 29,441
Short-term investments |  | 29,400
Long-term investments |  | $ 0
Commercial and corporate obligations | Minimum |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments outstanding, maturity date range (in years) |  | 1 year
Commercial and corporate obligations | Maximum |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments outstanding, maturity date range (in years) | 1 year | 2 years
US Treasury Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 45,680 | $ 107,530
Gross Unrealized Gains | 34 | 170
Gross Unrealized Losses | 0 | (3)
Total Fair Value | $ 45,714 | 107,697
Short-term investments |  | 102,700
Long-term investments |  | $ 5,000
US Treasury Securities | Minimum |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments outstanding, maturity date range (in years) |  | 1 year
US Treasury Securities | Maximum |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments outstanding, maturity date range (in years) |  | 2 years

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