Quarterly report pursuant to Section 13 or 15(d)

Convertible Senior Notes (Details)

v3.19.1
Convertible Senior Notes (Details)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Debt Instrument, Redemption [Line Items]    
Proceeds from convertible senior notes $ 282,200  
Convertible senior notes conversion ratio 0.0631227 0.0624003
Convertible senior notes $ 284,099 $ 283,856
Convertible Debt [Member]    
Debt Instrument, Redemption [Line Items]    
Convertible senior notes aggregate principal amount $ 287,500  
Convertible senior notes interest rate per annum 6.25%