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Investments - Schedule of Available-for-sale Investments (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Short-Term Marketable Securities    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost $ 292,556 $ 564,036
Unrealized Gain 88 809
Unrealized Loss (5) (12)
Estimated Fair Value 292,639 564,833
Long-Term Marketable Securities    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 217,455 118,429
Unrealized Gain 6 98
Unrealized Loss (82) (2)
Estimated Fair Value 217,379 118,525
U.S. Government Debt Securities | Short-Term Marketable Securities    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 277,331 552,539
Unrealized Gain 87 723
Unrealized Loss   (10)
Estimated Fair Value 277,418 553,252
U.S. Government Debt Securities | Long-Term Marketable Securities    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 204,694 118,429
Unrealized Gain 6 98
Unrealized Loss (74) (2)
Estimated Fair Value 204,626 118,525
Corporate Bonds | Short-Term Marketable Securities    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 15,225 11,497
Unrealized Gain 1 86
Unrealized Loss (5) (2)
Estimated Fair Value 15,221 $ 11,581
Corporate Bonds | Long-Term Marketable Securities    
Schedule of Available-for-Sale Securities [Line Items]    
Amortized Cost 12,761  
Unrealized Loss (8)  
Estimated Fair Value $ 12,753