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Fair Value Measurements - Additional Information (Details) - USD ($)
Sep. 30, 2019
Dec. 31, 2018
Revolving Credit Facility    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Line of credit $ 9,000,000.0  
Line of credit fair value 8,800,000  
Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Cash and cash equivalents 6,900,000  
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
Term Loans    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Debt instrument fair value 1,068,000,000  
Debt instrument carrying amount $ 1,075,000,000