Annual report pursuant to Section 13 and 15(d)

Income Taxes - Components of net income before income taxes (Details)

v3.8.0.1
Income Taxes - Components of net income before income taxes (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Components Of Net Income Before Income Taxes [Line Items]      
Net income before income taxes $ 770,614 $ 640,303 $ 433,909
Bermuda      
Components Of Net Income Before Income Taxes [Line Items]      
Net income before income taxes 0 0 0
Foreign - Other      
Components Of Net Income Before Income Taxes [Line Items]      
Net income before income taxes $ 770,614 $ 640,303 $ 433,909