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Fair Value Measurements - Additional Information (Details) - USD ($)
Mar. 31, 2019
Dec. 31, 2018
Revolving Credit Facility    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Line of credit $ 0  
Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Cash and cash equivalents 18,800,000  
Cash Convertible Notes Hedges and Cash Conversion Derivative    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Assets and liabilities measured at fair value on a recurring basis 0 $ 0
Term Loans    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Debt instrument fair value 1,146,000,000  
Debt instrument carrying amount $ 1,165,000,000