Taxation - Net Operating Loss Carryforwards (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Tax effect	$ 259,851	$ 255,151
Foreign Tax Authority | United States
Operating Loss Carryforwards [Line Items]
Loss Carryforwards	522,366
Tax effect	182,727
Foreign Tax Authority | United Kingdom
Operating Loss Carryforwards [Line Items]
Loss Carryforwards	333,814
Tax effect	66,763
Foreign Tax Authority | Other
Operating Loss Carryforwards [Line Items]
Loss Carryforwards	30,803
Tax effect	$ 10,361