v2.4.0.6
Fair Value, Investments in Entities That Calculate Net Asset Value Per Share (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Mar. 31, 2012
Dec. 31, 2011
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair value $ 1,349 $ 1,434
Unfunded commitments 257 268
Offshore Funds [Member]
   
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair value 329 352
Unfunded commitments 0 0
Redemption frequency Daily - Annually Daily - Annually
Redemption notice period 1 - 180 days 1 - 180 days
Funds of funds [Member]
   
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair value 1 1
Unfunded commitments 0 0
Redemption frequency Quarterly Quarterly
Redemption notice period 90 days 90 days
Hedge Funds [Member]
   
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair value 21 22
Unfunded commitments 0 0
Redemption frequency Daily - Annually Daily - Annually
Redemption notice period 5 - 95 days 5 - 95 days
Private equity [Member]
   
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair value 914 976
Unfunded commitments 232 240
Redemption frequency N/A N/A
Redemption notice period N/A N/A
Venture Capital Funds [Member]
   
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair value 84 83
Unfunded commitments $ 25 $ 28
Redemption frequency N/A N/A
Redemption notice period N/A N/A