Derivatives and Hedging Activites (Option Pay/Rec) (Details 3) $ in Millions	Jun. 30, 2016 USD ($)
Summary of Option Premiums Payable and Receivable
Premiums payable	$ 1,892
Premiums receivable	642
2016 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	163	[1]
Premiums receivable	38	[1]
2017 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	276
Premiums receivable	77
2018 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	225
Premiums receivable	132
2019 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	268
Premiums receivable	131
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	762
Premiums receivable	$ 205

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