Summary of Significant Accounting Policies - Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value of Financial Instruments
Money Market Funds	$ 143,480	$ 163,544
Marketable Securities	454,232
Equity Securities with Readily Determinable Fair Value	36,860	5,303
Money Market Funds
Fair Value of Financial Instruments
Money Market Funds	123,892	158,937
Corporate Securities
Fair Value of Financial Instruments
Marketable Securities	144,418	119,833
Government Securities
Fair Value of Financial Instruments
Marketable Securities	309,814	315,353
Fair Value, Measurements, Recurring
Fair Value of Financial Instruments
Total Fair Value	578,124	594,123
Fair Value, Measurements, Recurring \| Money Market Funds
Fair Value of Financial Instruments
Money Market Funds	123,892	158,937
Fair Value, Measurements, Recurring \| Corporate Securities
Fair Value of Financial Instruments
Marketable Securities	144,418	119,833
Fair Value, Measurements, Recurring \| Government Securities
Fair Value of Financial Instruments
Marketable Securities	309,814	315,353
Level 1 \| Fair Value, Measurements, Recurring
Fair Value of Financial Instruments
Total Fair Value	123,892	158,937
Level 1 \| Fair Value, Measurements, Recurring \| Money Market Funds
Fair Value of Financial Instruments
Money Market Funds	123,892	158,937
Level 2 \| Fair Value, Measurements, Recurring
Fair Value of Financial Instruments
Total Fair Value	454,232	435,186
Level 2 \| Fair Value, Measurements, Recurring \| Corporate Securities
Fair Value of Financial Instruments
Marketable Securities	144,418	119,833
Level 2 \| Fair Value, Measurements, Recurring \| Government Securities
Fair Value of Financial Instruments
Marketable Securities	$ 309,814	$ 315,353

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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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