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Convertible Senior Notes - Narrative (Details) - Convertible Debt - Convertible Notes
$ / shares in Units, $ in Thousands
Nov. 15, 2018
USD ($)
$ / shares
Sep. 30, 2019
USD ($)
Dec. 31, 2018
USD ($)
Debt Instrument [Line Items]      
Face Amount | $ $ 210,000 $ 210,000 $ 210,000
Interest Rate 6.25%    
Conversion rate 0.0520183    
Conversion Price | $ / shares $ 19.22