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Fair Value Measurements - Schedule of Cash and Available-for-sale Debt Securities' Amortized Cost, Unrealized Gains (Losses) and Fair Value by Significant Investment Category (Details) - USD ($)
Sep. 30, 2024
Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Amortized Cost $ 182,883,000 $ 86,864,000
Amortized Cost 1,818,952,000 1,676,044,000
Unrealized Gain 7,999,000 3,078,000
Unrealized (Loss) (82,000) (1,018,000)
Fair Value 1,826,869,000 1,678,104,000
Cash    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Amortized Cost 70,313,000 51,189,000
Unrealized Gain 0 0
Unrealized (Loss) 0 0
Fair Value 70,313,000 51,189,000
Money market funds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Unrealized Gain 0 0
Unrealized (Loss) 0 0
Level I | Money market funds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Amortized Cost 100,666,000 40,035,000
Unrealized Gain 0 0
Unrealized (Loss) 0 0
Fair Value 100,666,000 40,035,000
Level II    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Amortized Cost 1,647,973,000 1,584,820,000
Unrealized Gain 7,999,000 3,078,000
Unrealized (Loss) (82,000) (1,018,000)
Fair Value 1,655,890,000 1,586,880,000
Level II | Corporate bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Amortized Cost 426,692,000 312,510,000
Unrealized Gain 2,613,000 718,000
Unrealized (Loss) (17,000) (378,000)
Fair Value 429,288,000 312,850,000
Level II | U.S. treasury securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Amortized Cost 1,084,326,000 1,020,167,000
Unrealized Gain 5,183,000 2,344,000
Unrealized (Loss) (52,000) (544,000)
Fair Value 1,089,457,000 1,021,967,000
Level II | U.S. government agency securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Amortized Cost 76,775,000 84,154,000
Unrealized Gain 203,000 14,000
Unrealized (Loss) (13,000) (96,000)
Fair Value 76,965,000 84,072,000
Level II | Commercial paper    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Amortized Cost 60,180,000 167,989,000
Unrealized Gain 0 2,000
Unrealized (Loss) 0 0
Fair Value 60,180,000 167,991,000
Cash & Cash Equivalents | Fair Value, Recurring    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total assets measured at fair value on a recurring basis 182,883,000 86,864,000
Cash & Cash Equivalents | Fair Value, Recurring | Cash    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 67,290,000 46,829,000
Cash & Cash Equivalents | Fair Value, Recurring | Level I | Money market funds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 100,666,000 40,035,000
Cash & Cash Equivalents | Fair Value, Recurring | Level II    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 14,927,000 0
Cash & Cash Equivalents | Fair Value, Recurring | Level II | Corporate bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Cash & Cash Equivalents | Fair Value, Recurring | Level II | U.S. treasury securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 14,927,000 0
Cash & Cash Equivalents | Fair Value, Recurring | Level II | U.S. government agency securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Cash & Cash Equivalents | Fair Value, Recurring | Level II | Commercial paper    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Available-for-sale securities | Fair Value, Recurring    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 1,640,963,000 1,586,880,000
Available-for-sale securities | Fair Value, Recurring | Cash    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Available-for-sale securities | Fair Value, Recurring | Level I | Money market funds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Available-for-sale securities | Fair Value, Recurring | Level II    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 1,640,963,000 1,586,880,000
Available-for-sale securities | Fair Value, Recurring | Level II | Corporate bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 429,288,000 312,850,000
Available-for-sale securities | Fair Value, Recurring | Level II | U.S. treasury securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 1,074,530,000 1,021,967,000
Available-for-sale securities | Fair Value, Recurring | Level II | U.S. government agency securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 76,965,000 84,072,000
Available-for-sale securities | Fair Value, Recurring | Level II | Commercial paper    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 60,180,000 167,991,000
Restricted Cash (Current and Non-Current) | Fair Value, Recurring    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total assets measured at fair value on a recurring basis 3,023,000 4,360,000
Restricted Cash (Current and Non-Current) | Fair Value, Recurring | Cash    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 3,023,000 4,360,000
Restricted Cash (Current and Non-Current) | Fair Value, Recurring | Level I | Money market funds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Restricted Cash (Current and Non-Current) | Fair Value, Recurring | Level II    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Restricted Cash (Current and Non-Current) | Fair Value, Recurring | Level II | Corporate bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Restricted Cash (Current and Non-Current) | Fair Value, Recurring | Level II | U.S. treasury securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Restricted Cash (Current and Non-Current) | Fair Value, Recurring | Level II | U.S. government agency securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value 0 0
Restricted Cash (Current and Non-Current) | Fair Value, Recurring | Level II | Commercial paper    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair Value $ 0 $ 0