Fair Value Measurements - Fair Value of Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private Common Stock Warrants	$ 1,831	$ 6,293
Fair Value, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	573,562	528,902
Total liabilities	1,831	6,293
Fair Value, Recurring | Asset backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	113,038	111,552
Fair Value, Recurring | Certificates of deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	6,000	6,002
Fair Value, Recurring | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	234,237	206,989
Fair Value, Recurring | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	129,202	109,391
Fair Value, Recurring | Foreign government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	18,151	8,181
Fair Value, Recurring | US Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	72,933	86,787
Fair Value, Recurring | Private Common Stock Warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private Common Stock Warrants	1,831	6,293
Level 1 | Fair Value, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	44,974	86,787
Total liabilities	0	0
Level 1 | Fair Value, Recurring | Asset backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 1 | Fair Value, Recurring | Certificates of deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 1 | Fair Value, Recurring | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 1 | Fair Value, Recurring | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 1 | Fair Value, Recurring | Foreign government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 1 | Fair Value, Recurring | US Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	44,974	86,787
Level 1 | Fair Value, Recurring | Private Common Stock Warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private Common Stock Warrants	0	0
Level 2 | Fair Value, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	528,588	442,114
Total liabilities	0	0
Level 2 | Fair Value, Recurring | Asset backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	113,038	111,552
Level 2 | Fair Value, Recurring | Certificates of deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	6,000	6,002
Level 2 | Fair Value, Recurring | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	234,237	206,989
Level 2 | Fair Value, Recurring | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	129,202	109,391
Level 2 | Fair Value, Recurring | Foreign government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	18,151	8,181
Level 2 | Fair Value, Recurring | US Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	27,959	0
Level 2 | Fair Value, Recurring | Private Common Stock Warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private Common Stock Warrants	0	0
Level 3 | Fair Value, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Total liabilities	1,831	6,293
Level 3 | Fair Value, Recurring | Asset backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 3 | Fair Value, Recurring | Certificates of deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 3 | Fair Value, Recurring | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 3 | Fair Value, Recurring | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 3 | Fair Value, Recurring | Foreign government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 3 | Fair Value, Recurring | US Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-Sale Investments	0	0
Level 3 | Fair Value, Recurring | Private Common Stock Warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Private Common Stock Warrants	$ 1,831	$ 6,293