Derivatives and Hedging Activities (Option Pay/Rec) (Details 3) $ in Millions	Dec. 31, 2015 USD ($)
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable for derivative option contracts	$ 1,920
Premiums receivable for derivative option contracts	641
2016 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable for derivative option contracts	331
Premiums receivable for derivative option contracts	76
2017 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable for derivative option contracts	273
Premiums receivable for derivative option contracts	76
2018 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable for derivative option contracts	221
Premiums receivable for derivative option contracts	126
2018 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable for derivative option contracts	264
Premiums receivable for derivative option contracts	128
2019 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable for derivative option contracts	198
Premiums receivable for derivative option contracts	59
2020-2027 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable for derivative option contracts	633
Premiums receivable for derivative option contracts	$ 176