Quarterly report pursuant to Section 13 or 15(d)

Debt (CredAg) (Details)

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Debt (CredAg) (Details) - USD ($)
$ in Thousands
9 Months Ended
Jul. 18, 2017
Sep. 30, 2017
Dec. 31, 2016
Debt      
Amount outstanding   $ 101,168  
Term Notes      
Debt      
Face amount     $ 142,000
Second Amended and Restated Credit Agreement      
Debt      
Credit facility amount $ 350,000    
Right to increase credit facility, amount $ 50,000    
Voting equity of foreign subsidiary pledged (as a percent) 66.00%    
Non-voting equity of foreign subsidiary pledged (as a percent) 100.00%    
Amount outstanding   $ 101,168  
Letters of credit      
Debt      
Credit facility amount $ 5,000    
Minimum | Second Amended and Restated Credit Agreement | LIBOR      
Debt      
Spread on variable rate basis (as a percent)   1.50%  
Maximum | Second Amended and Restated Credit Agreement | LIBOR      
Debt      
Spread on variable rate basis (as a percent)   3.25%