Fair Value of Financial Instruments - Schedule of Estimated Fair Values of Financial Instruments Outstanding (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Cost	$ 21,242
Unrealized Gains	0
Unrealized Losses	(6)
Fair Value	21,236
Cash and Cash Equivalents
Debt Securities, Available-for-sale [Line Items]
Cost	9,820	$ 5,889
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	9,820	$ 5,889
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Cost	8,216
Unrealized Gains	0
Unrealized Losses	(3)
Fair Value	8,213
Long-term investments
Debt Securities, Available-for-sale [Line Items]
Cost	3,206
Unrealized Gains	0
Unrealized Losses	(3)
Fair Value	$ 3,203

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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