Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation (Details)

v3.19.1
Basis of Presentation (Details) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Mar. 31, 2018
Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]        
Cash and cash equivalents $ 245,735 $ 289,345    
Restricted cash 158 158    
Total cash, cash equivalents and restricted cash 246,061 289,671 $ 46,193 $ 62,115
Prepaid Expenses and Other Current Assets        
Restricted Cash and Cash Equivalents Items [Line Items]        
Restricted cash 158 158    
Other Noncurrent Assets        
Restricted Cash and Cash Equivalents Items [Line Items]        
Restricted cash $ 168 $ 168