XML 72 R66.htm IDEA: XBRL DOCUMENT v2.4.0.6
Employee Share-Based Incentive Compensation Plans (Details 6) (OneBeacon Restricted Stock, USD $)
In Millions, except Share data, unless otherwise specified
 3 Months Ended 6 Months Ended 1 Months Ended 3 Months Ended 1 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
May 31, 2011
OneBeacon Long-Term Incentive Plan
Mar. 31, 2008
OneBeacon Long-Term Incentive Plan
Mar. 31, 2012
OneBeacon Long-Term Incentive Plan
Mar. 01, 2012
OneBeacon Long-Term Incentive Plan
Installment
May 31, 2011
OneBeacon Long-Term Incentive Plan
Chairman and CEO
Year
May 25, 2011
OneBeacon Long-Term Incentive Plan
Chairman and CEO
Installment
Share-based compensation arrangement by share-based payment award                    
Total number of performance share grants to be reduced         35,000       35,000  
Number of installments in which the shares vest               2   4
Activity in plan                    
Beginning of period (in shares) 930,000 0 630,000 0            
Issued (in shares) 0 630,000 300,000 630,000     300,000   630,000  
Ending of period (in shares) 930,000 630,000 930,000 630,000            
Unamortized grant date fair value                    
Unamortized grant date fair value, beginning balance $ 11.9 $ 0 $ 7.7 $ 0            
Issued 0 8.6 4.6 8.6            
Expense recognized (0.7) (0.1) (1.1) (0.1)            
Unamortized grant date fair value, ending balance 11.2 8.5 11.2 8.5            
New grants (in shares)           116,270        
Minimum percentage of growth in book value per share for vesting each tranche of units           4.00%        
Expense recognized (0.7) (0.1) (1.1) (0.1)            
Period in which performance share awards will be reduced by a similar number of shares (in years)                 5  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period 0 0 0 0            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value 0 0 0 0            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period 0 0 0 0            
Employee Service Share-based Compensation Nonvested Awards Forfeited in Period Total Compensation Cost Not yet Recognized $ 0 $ 0 $ 0 $ 0