XML 96 R78.htm IDEA: XBRL DOCUMENT v3.7.0.1
Derivatives (Value, Collateral (held) provided by WM Life Re and Net Exposure to Credit Losses on OTC Derivative Instruments) (Details) - White Mountains Life Re
$ in Millions
Mar. 31, 2016
USD ($)
Offsetting Liabilities [Line Items]  
Derivative Assets $ 16.7
Derivative Liabilities (3.6)
Net amounts recognized in Other assets 13.1
Over The Counter | Fixed income/interest rate  
Offsetting Liabilities [Line Items]  
Derivative Assets 2.2
Derivative Liabilities (2.5)
Net amounts recognized in Other assets (0.3)
Over The Counter | Foreign exchange  
Offsetting Liabilities [Line Items]  
Derivative Assets 12.7
Derivative Liabilities 0.0
Net amounts recognized in Other assets 12.7
Over The Counter | Equity  
Offsetting Liabilities [Line Items]  
Derivative Assets 1.5
Derivative Liabilities (0.9)
Net amounts recognized in Other assets 0.6
Exchange Traded | Foreign exchange  
Offsetting Liabilities [Line Items]  
Derivative Assets 0.0
Derivative Liabilities (0.1)
Net amounts recognized in Other assets (0.1)
Exchange Traded | Equity  
Offsetting Liabilities [Line Items]  
Derivative Assets 0.3
Derivative Liabilities (0.1)
Net amounts recognized in Other assets $ 0.2