v3.2.0.727
Commitments, contingencies, and guarantees Commitments, Contingencies, And Guarantees (Collateral pledged under repurchase agreements) (Details) - USD ($)
$ in Millions
Jun. 30, 2015
Dec. 31, 2014
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Securities Sold under Agreements to Repurchase $ 1,402 $ 1,402
Assets pledged under repurchase agreements 1,458 1,431
Securities lending collateral 1,080 1,330
Securities lending payable 1,081 $ 1,331
Cash and Cash Equivalents [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 5  
U.S. Treasury And Agency [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 238  
Collateralized Mortgage Backed Securities [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 1,215  
Repurchase Agreements [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Secured Borrowings, Gross, Difference, Amount [1] 56  
Overnight and Continuous [Member] | Cash and Cash Equivalents [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Securities lending collateral 526  
Overnight and Continuous [Member] | Foreign [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Securities lending collateral 477  
Overnight and Continuous [Member] | Corporate Securities [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Securities lending collateral 3  
Overnight and Continuous [Member] | U.S. Treasury And Agency [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Securities lending collateral 74  
30 to 90 Days [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 148  
30 to 90 Days [Member] | Cash and Cash Equivalents [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 0  
30 to 90 Days [Member] | U.S. Treasury And Agency [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 62  
30 to 90 Days [Member] | Collateralized Mortgage Backed Securities [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 86  
Greater than 90 Days [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 1,310  
Greater than 90 Days [Member] | Cash and Cash Equivalents [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 5  
Greater than 90 Days [Member] | U.S. Treasury And Agency [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements 176  
Greater than 90 Days [Member] | Collateralized Mortgage Backed Securities [Member]    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Assets pledged under repurchase agreements $ 1,129  
[1] Per the repurchase agreements, the amount of collateral posted is required to exceed the amount of gross liability.