v2.4.0.6
Fair Value Disclosures (Fair Value of Investments that Calculate Net Asset Value) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Investments $ 8,346 $ 8,195
Fair Value 4,489 4,261
Unfunded Commitment 868 1,391
Private Equity Funds
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 2,179 1,906
Unfunded Commitment 644 938
Percent of investments that will be liquidated in the next five years 5.00%  
Percent of investments that will be liquidated within five to 10 years 27.00%  
Percent of investments that will be liquidated after 10 years 68.00%  
Real Estate Funds
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 1,376 1,188
Unfunded Commitment 221 448
Percent of investments that will be liquidated in the next five years 4.00%  
Percent of investments that will be liquidated within five to 10 years 46.00%  
Percent of investments that will be liquidated after 10 years 50.00%  
Hedge Funds
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Redemption frequency at least on a six-month period basis  
Redemption notice period 90 days or less  
Long-short Equity Hedge Funds
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 475 [1] 545 [1]
Unfunded Commitment 0 [1] 5 [1]
Redemption notice period primarily greater than six months primarily greater than six months
Percent of investments redeemable at least quarterly 36.00% 38.00%
Percent of investments redeemable every six months 38.00% 32.00%
Percent of investments redeemable greater than six months 26.00% 30.00%
Long-short Equity Hedge Funds | Initial Period Lock-up Restrictions
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Percent of investments that cannot be redeemed currently 7.00%  
Long-short Equity Hedge Funds | Subsequent Lock-up Restrictions
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Redemption restriction period two years or less  
Long-short Equity Hedge Funds | Exit Restrictions
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Percent of investments that cannot be redeemed currently 7.00%  
Redemption restriction period one year or less  
Fixed Income/Credit-Related Hedge Funds
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 86 [1] 124 [1]
Unfunded Commitment 0 [1] 0 [1]
Fixed Income/Credit-Related Hedge Funds | Initial Period Lock-up Restrictions
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Percent of investments that cannot be redeemed currently 5.00%  
Fixed Income/Credit-Related Hedge Funds | Subsequent Lock-up Restrictions
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Redemption restriction period one year or less  
Event Driven Hedge Funds
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 52 [1] 163 [1]
Unfunded Commitment 0 [1] 0 [1]
Multi-strategy Hedge Funds
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Fair Value 321 [1] 335 [1]
Unfunded Commitment $ 3 [1] $ 0 [1]
Multi-strategy Hedge Funds | Initial Period Lock-up Restrictions
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Percent of investments that cannot be redeemed currently 66.00%  
Multi-strategy Hedge Funds | Subsequent Lock-up Restrictions
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Redemption restriction period primarily two years or less  
Multi-strategy Hedge Funds | Exit Restrictions
    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]    
Percent of investments that cannot be redeemed currently 9.00%  
[1] Fixed income/credit-related hedge funds, event-driven hedge funds, and multi-strategy hedge funds are redeemable at least on a six-month period basis primarily with a notice period of 90 days or less. At December 31, 2012, approximately 36% of the fair value amount of long-short equity hedge funds is redeemable at least quarterly, 38% is redeemable every six months and 26% of these funds have a redemption frequency of greater than six months. The notice period for long-short equity hedge funds at December 31, 2012 is primarily greater than six months. At December 31, 2011, approximately 38% of the fair value amount of long-short equity hedge funds is redeemable at least quarterly, 32% is redeemable every six months and 30% of these funds have a redemption frequency of greater than six months. The notice period for long-short equity hedge funds at December 31, 2011 is primarily greater than six months.