Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Earnings per share (Computations of basic and diluted earnings per share) (Details)

v3.8.0.1
Earnings per share (Computations of basic and diluted earnings per share) (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Earnings Per Share [Abstract]      
Net income for the computation of basic EPS $ 1,076,151 $ 1,046,630 $ 1,178,730
Weighted average ordinary shares outstanding - basic (in shares) 161,059,552 185,514,370 203,850,828
Basic earnings per share (in USD per share) $ 6.68 $ 5.64 $ 5.78
Weighted average ordinary shares outstanding - diluted (in shares) 167,287,508 189,682,036 206,224,135
Diluted earnings per share (in USD per share) $ 6.43 $ 5.52 $ 5.72