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Equity (Details) - USD ($)
$ in Thousands, shares in Millions
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Oct. 27, 2016
Purchase of treasury stock $ 13,569 $ 13,720  
Treasury Stock [Member]      
Purchase of treasury stock $ 13,569 $ 13,720  
Class B [Member]      
Number of shares authorized under share repurchase program     4.0
Repurchased shares 0.5    
Remaining number of shares authorized to be repurchased 3.4