Derivatives and Hedging Activites (Option Pay/Rec) (Details 3) $ in Millions	Sep. 30, 2016 USD ($)
Summary of Option Premiums Payable and Receivable
Premiums payable	$ 1,911
Premiums receivable	637
2016 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	92	[1]
Premiums receivable	31	[1]
2017 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	277
Premiums receivable	77
2018 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	233
Premiums receivable	132
2019 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	280
Premiums receivable	132
2020 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	198
Premiums receivable	59
2021-2027 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	831
Premiums receivable	$ 206

[1] 2016 amounts represent the amounts payable and receivable for the period from October 1, 2016 to December 31, 2016.