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Share Capital - Additional Information (Details) - USD ($)
 12 Months Ended 27 Months Ended
Jul. 31, 2015
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2018
Oct. 03, 2016
Equity, Class of Treasury Stock [Line Items]              
Total proceeds from exercise of stock options by employees   $ 16,842,000 $ 13,950,000 $ 10,180,000      
Ordinary shares redeemed, value   $ 128,960,000 $ 133,106,000 $ 110,000,000      
Employee Stock Option              
Equity, Class of Treasury Stock [Line Items]              
Options exercised by employees (in shares)   408,699 458,243 393,240      
Average exercise price of option per share (usd per share)   $ 41.12 $ 30.35 $ 25.79      
Total proceeds from exercise of stock options by employees   $ 16,800,000 $ 13,900,000 $ 10,100,000      
Restricted Stock Units (RSUs)              
Equity, Class of Treasury Stock [Line Items]              
Ordinary shares issued in respect of certain RSUs previously awarded by the Company (in shares)   276,495 361,102 296,386      
Performance Share Unit (PSUs)              
Equity, Class of Treasury Stock [Line Items]              
Ordinary shares issued in respect of certain PSUs previously awarded by the Company (in shares)   215,826 320,640 311,492      
Buyback Program              
Equity, Class of Treasury Stock [Line Items]              
Stock repurchase program, authorized amount $ 400,000,000           $ 400,000,000
Ordinary shares redeemed (in shares) 5,316,062 1,008,162     6,198,481 4,026,576  
Ordinary shares redeemed, value $ 400,000,000 $ 129,000,000     $ 457,900,000 $ 372,100,000