Basis of Presentation and Summary of Significant Accounting Policies - Investment Categories (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 257,266	$ 324,567
Gross unrealized gains	1,070	1,302
Gross unrealized losses	(726)	(1,391)
Estimated fair value	257,610	324,478
Estimated fair value	299,781	363,567
Bank deposits
Debt Securities, Available-for-sale [Line Items]
Amortized cost	47,739	84,120
Gross unrealized gains	8	35
Gross unrealized losses	(3)	(1)
Estimated fair value	47,744	84,154
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized cost	25,914	30,512
Gross unrealized gains	50	99
Gross unrealized losses	0	(1)
Estimated fair value	25,964	30,610
Agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized cost	2,501	4,499
Gross unrealized gains	0	2
Gross unrealized losses	0	0
Estimated fair value	2,501	4,501
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized cost	23,264	45,459
Gross unrealized gains	10	27
Gross unrealized losses	0	(1)
Estimated fair value	23,274	45,485
Corporate equity securities
Debt Securities, Available-for-sale [Line Items]
Amortized cost	5,807	4,466
Gross unrealized gains	307	360
Gross unrealized losses	(723)	(1,388)
Estimated fair value	5,391	3,438
Mutual fund
Debt Securities, Available-for-sale [Line Items]
Amortized cost	152,041	151,512
Gross unrealized gains	53	386
Gross unrealized losses	0	0
Estimated fair value	152,094	151,898
Treasury bill
Debt Securities, Available-for-sale [Line Items]
Amortized cost	0	3,999
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated fair value	0	3,999
Warrants
Debt Securities, Available-for-sale [Line Items]
Amortized cost	0	0
Gross unrealized gains	642	393
Gross unrealized losses	0	0
Estimated fair value	642	393
Estimated fair value	0	6,326
Common Stock
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	$ 42,171	$ 32,763

Debt Securities, Available for Sale and Equity Securities, FV-NI

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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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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 investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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