Annual report pursuant to Section 13 and 15(d)

Employee Benefits (Details)

v3.8.0.1
Employee Benefits (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
401(k)      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Employer matching contribution percent 100.00%    
Employer matching percent 6.00%    
Employer contributions $ 3,832 $ 4,600 $ 4,733
GPPP | United Kingdom      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Employer matching contribution percent 100.00%    
Employer matching percent 6.00%    
Employer contributions $ 344 202  
RRSP | Canada      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Employer matching contribution percent 100.00%    
Employer matching percent 6.00%    
Employer contributions $ 774 $ 307 $ 411