Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation (Details)

v3.19.2
Basis of Presentation (Details) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Jun. 30, 2018
Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]        
Cash and cash equivalents $ 77,717 $ 289,345    
Total cash, cash equivalents and restricted cash 78,043 289,671 $ 134,260 $ 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