Quarterly report pursuant to Section 13 or 15(d)

Share Repurchase Program (Details)

v3.10.0.1
Share Repurchase Program (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended 15 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Feb. 28, 2017
Sep. 30, 2018
Jul. 05, 2017
Feb. 24, 2017
Number of shares repurchased (in shares) 142,780 1,507,443 156,437 2,365,836        
Share repurchase cost $ 9,493 $ 100,000   $ 139,286        
Average price per share (in dollars per share) $ 66.49 $ 66.34   $ 58.87        
2016 Repurchase program                
Number of shares repurchased (in shares)         788,399      
Share repurchase cost         $ 26,600      
Average price per share (in dollars per share)         $ 33.72      
2017 Repurchase program                
Number of shares repurchased (in shares)     142,780          
Average price per share (in dollars per share)     $ 66.49          
2017 ASR Agreement                
Number of shares repurchased (in shares)     13,657     1,521,100    
Average price per share (in dollars per share)           $ 65.74    
Payment under ASR agreement             $ 100,000  
Initial number of shares delivered under ASR agreement (in shares)             1,500,000  
Initial percentage of shares delivered under ASR agreement             80.00%  
Maximum | 2017 Repurchase program                
Share repurchase program, authorized amount               $ 200,000