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Fair Value Measurement - Narrative (Details) - USD ($)
$ in Millions
Mar. 31, 2020
Feb. 15, 2018
Feb. 15, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Equity securities without readily determinable fair value $ 4.5    
2021 Notes | Convertible Debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Interest rate (as a percent)     1.875%
2024 Notes | Convertible Debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Interest rate (as a percent)   1.50%  
Significant Other Observable Inputs (Level 2) | 2021 Notes | Convertible Debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Fair value of exchangeable senior notes 550.0    
Significant Other Observable Inputs (Level 2) | 2024 Notes | Convertible Debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Fair value of exchangeable senior notes $ 502.0