Debt (Schedule of FHLB, Advances, Maturity Summary) (Details) - USD ($)
$ in Millions
Sep. 30, 2016
Dec. 31, 2015
Debt Disclosure [Abstract]    
2016 $ 1,030  
2017 50  
2018 125  
2019 0  
Thereafter 1,277  
Federal Home Loan Bank Advances $ 2,482 $ 3,541