XML 71 R60.htm IDEA: XBRL DOCUMENT v3.19.1
Debt - Convertible Notes (Details) - 3.00% Convertible senior notes due 2022 - Convertible debt - USD ($)
Mar. 31, 2019
Dec. 31, 2018
Aug. 31, 2015
Long-term debt      
Principal $ 150,000,000 $ 150,000,000 $ 150,000,000.0
Less: Debt issuance costs (1,648,000) (1,746,000)  
Less: Debt discount, net (33,072,000) (35,054,000)  
Net carrying amount $ 115,280,000 $ 113,200,000