v3.3.1.900
Taxation - Tax Rate Reconciliation (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Tax Disclosure [Abstract]                      
Income before income taxes                 $ 126,322 $ 103,697 $ 104,719
Income tax expense                 2,038 2,164 1,863
Net income $ 30,724 $ 28,515 $ 26,511 $ 38,534 $ 33,631 $ 33,926 $ 31,915 $ 2,061 $ 124,284 $ 101,533 $ 102,856
Reconciliation of effective tax rate (% of income before income taxes)                      
Bermuda tax rate                 0.00% 0.00% 0.00%
U.S. taxes at statutory rates                 (2.20%) (7.30%) (8.70%)
Valuation allowance in respect of U.S. taxes                 3.20% 8.50% 9.80%
Other jurisdictions                 0.60% 0.90% 0.70%
Actual tax rate                 1.60% 2.10% 1.80%