XML 149 R137.htm IDEA: XBRL DOCUMENT v3.10.0.1
Note Stockholders' equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Dec. 31, 2016
Stockholders Equity Note [Line Items]            
Dividends, Common Stock, Cash     $ 76,200 $ 76,620    
Dividends Payable $ 25,100   25,100      
Stockholders Equity $ 5,244,349 $ 5,285,431 $ 5,244,349 5,285,431 $ 5,103,905 $ 5,197,957
Dividend payable, to be paid date     Oct. 01, 2018      
Dividends payable, record date     Aug. 23, 2018      
Initial shares received as part of an accelerated share repurchase program 2,000,000          
Common stock purchases     $ 127,443 $ 77,418    
Dividends Declared per Common Share $ 0.25 $ 0.25 $ 0.75 $ 0.75    
Accelerated share repurchases settlement receipt $ 125,000   $ 125,000      
Treasury Stock            
Stockholders Equity Note [Line Items]            
Stockholders Equity (183,872) $ (90,222) (183,872) $ (90,222) (90,142) (8,286)
Common stock purchases     104,423 81,936    
Surplus            
Stockholders Equity Note [Line Items]            
Stockholders Equity 4,281,515 $ 4,265,053 4,281,515 4,265,053 $ 4,298,503 $ 4,255,022
Common stock purchases     $ 23,020 $ (4,518)    
Accelerate Share Repurchase Transaction | Treasury Stock            
Stockholders Equity Note [Line Items]            
Common stock purchases 102,000          
Accelerate Share Repurchase Transaction | Surplus            
Stockholders Equity Note [Line Items]            
Common stock purchases $ 23,000