Derivatives and Hedging Activites (Option Pay/Rec) (Details 4) $ in Millions	Sep. 30, 2015 USD ($)
Summary of Option Premiums Payable and Receivable
Premiums payable	$ 2,004
Premiums receivable	638
Current Year [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	110	[1]
Premiums receivable	28	[1]
2016 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	346
Premiums receivable	77
2017 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	286
Premiums receivable	77
2018 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	227
Premiums receivable	126
2019 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	274
Premiums receivable	103
2020-2027 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	761
Premiums receivable	$ 227

[1] 2015 amounts represent the amounts payable and receivable for the period from October 1, 2015 to December 31, 2015.