Quarterly report pursuant to Section 13 or 15(d)

Employee Benefits and Compensation Plans - Summary of Share Option Awards (Details)

v3.8.0.1
Employee Benefits and Compensation Plans - Summary of Share Option Awards (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Additional General Disclosures [Abstract]    
Options Outstanding, Weighted- Average Contractual Term 6 years 11 months 27 days 6 years 9 months 7 days
Options Outstanding, Aggregate Intrinsic Value $ 50,021 $ 47,171
Time Based Options    
Number of Share Option Awards    
Outstanding as of January 1, 2018 6,580,898  
Granted 0  
Exercised (117,805)  
Forfeited and cancelled (60,083)  
Outstanding as of March 31, 2018 6,403,010 6,580,898
Weighted-Average Exercise Price    
Outstanding as of January 1, 2018 $ 49.18  
Granted 0.00  
Exercised 39.27  
Forfeited and cancelled 52.08  
Outstanding as of March 31, 2018 $ 49.34 $ 49.18
Performance Based Options    
Number of Share Option Awards    
Outstanding as of January 1, 2018 373,969  
Granted 208,335  
Exercised 0  
Forfeited and cancelled (52,084)  
Outstanding as of March 31, 2018 530,220 373,969
Weighted-Average Exercise Price    
Outstanding as of January 1, 2018 $ 31.39  
Granted 59.43  
Exercised 0.00  
Forfeited and cancelled 59.43  
Outstanding as of March 31, 2018 $ 39.65 $ 31.39
Market-Based Awards    
Number of Share Option Awards    
Outstanding as of January 1, 2018 208,333  
Granted 0  
Exercised 0  
Forfeited and cancelled 0  
Outstanding as of March 31, 2018 208,333 208,333
Weighted-Average Exercise Price    
Outstanding as of January 1, 2018 $ 59.43  
Granted 0.00  
Exercised 0.00  
Forfeited and cancelled 0.00  
Outstanding as of March 31, 2018 $ 59.43 $ 59.43