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Fair Value Measurements (Details) - USD ($)
$ in Thousands
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2016
3.75% Convertible notes due 2023      
Liabilities      
Coupon interest rate     3.75%
5.00% Convertible notes due 2027 | Unsecured Debt      
Liabilities      
Coupon interest rate 5.00%    
Level 1      
Assets      
Total cash equivalents $ 398,834 $ 361,822  
Liabilities      
Total convertible notes payable 0 0  
Level 1 | 3.75% Convertible notes due 2023      
Liabilities      
Total convertible notes payable 0 0  
Level 1 | 5.00% Convertible notes due 2027      
Liabilities      
Total convertible notes payable 0 0  
Level 1 | Money market funds      
Assets      
Total cash equivalents 398,834 361,822  
Level 1 | Government-backed securities      
Assets      
Total cash equivalents 0 0  
Level 1 | Corporate debt securities      
Assets      
Total cash equivalents 0 0  
Level 1 | Agency securities      
Assets      
Total cash equivalents 0 0  
Level 2      
Assets      
Total cash equivalents 400,536 1,056,922  
Liabilities      
Total convertible notes payable 494,900 447,509  
Level 2 | 3.75% Convertible notes due 2023      
Liabilities      
Total convertible notes payable 322,111 447,509  
Level 2 | 5.00% Convertible notes due 2027      
Liabilities      
Total convertible notes payable 172,789 0  
Level 2 | Money market funds      
Assets      
Total cash equivalents 0 0  
Level 2 | Government-backed securities      
Assets      
Total cash equivalents 296,000 266,250  
Level 2 | Corporate debt securities      
Assets      
Total cash equivalents 0 790,672  
Level 2 | Agency securities      
Assets      
Total cash equivalents 104,536 0  
Level 3      
Assets      
Total cash equivalents 0 0  
Liabilities      
Total convertible notes payable 0 0  
Level 3 | 3.75% Convertible notes due 2023      
Liabilities      
Total convertible notes payable 0 0  
Level 3 | 5.00% Convertible notes due 2027      
Liabilities      
Total convertible notes payable 0 0  
Level 3 | Money market funds      
Assets      
Total cash equivalents 0 0  
Level 3 | Government-backed securities      
Assets      
Total cash equivalents 0 0  
Level 3 | Corporate debt securities      
Assets      
Total cash equivalents 0 0  
Level 3 | Agency securities      
Assets      
Total cash equivalents $ 0 $ 0