Financial Instruments and Fair Value Measurements - Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Available-for-Sale Securities
Amortized Cost	$ 78,025	$ 204,808
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	78,025	204,808
Credit loss	0	0
Money market funds
Available-for-Sale Securities
Amortized Cost	78,025	204,808
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 78,025	$ 204,808

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).

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Amount of allowance for credit loss 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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