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Investments and Fair Value Measurements - Narrative (Details) - USD ($)
3 Months Ended
Mar. 31, 2020
Dec. 31, 2019
May 31, 2018
Debt Instrument [Line Items]      
Impairment loss on available-for-sale debt securities $ 0    
Level 2 | Convertible debt      
Debt Instrument [Line Items]      
Fair value of long-term debt 493,200,000 $ 437,000,000.0  
Nonrecurring      
Debt Instrument [Line Items]      
Assets measured at fair value on nonrecurring basis 0 0  
Liabilities measured at fair value on nonrecurring basis $ 0 $ 0  
Convertible Senior Notes | Convertible debt      
Debt Instrument [Line Items]      
Stated interest rate on debt (percent) 0.125% 0.125% 0.125%