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Cash Equivalents and Investments - Narrative (Details)
12 Months Ended
Dec. 31, 2019
USD ($)
Investment
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Oct. 31, 2019
USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]        
Total investments In unrealized loss position | Investment 179      
OTTI, associated with credit losses $ 0      
Available-for-sale debt securities, gross realized gain 0 $ 0 $ 0  
Available-for-sale debt securities, gross realized losses 0 0 0  
Equity ownership, cost method       $ 89,900,000
Equity investments, unrealized gains 0 0 0  
Equity investments, unrealized losses 0 0 0  
Restricted cash and investments 91,600,000      
Prepaid expenses and other current assets        
Restricted Cash and Cash Equivalents Items [Line Items]        
Restricted cash and investments 64,600,000      
Other long-term assets        
Restricted Cash and Cash Equivalents Items [Line Items]        
Restricted cash and investments 27,000,000.0      
Debt Securities        
Restricted Cash and Cash Equivalents Items [Line Items]        
OTTI, associated with credit losses $ 0 $ 0 $ 0  
Privately-held company        
Restricted Cash and Cash Equivalents Items [Line Items]        
Ownership interest, percentage       13.70%