Derivative Instruments and Other Financial Instruments Used For Hedging (Details 5) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Financial Assets
Gross Amounts of Recognized Assets, Derivative assets	$ 2,339	$ 1,828
Gross Amounts Offset in Balance Sheet, Derivative assets	1,042	909
Net Amounts Presented in Balance Sheet, Derivative assets	1,297	919
Gross Amounts Not Offset In Balance Sheet, Financial Instruments, Derivative assets	55	60
Net Amount, Derivative assets	1,240	859
Gross Amounts of Recognized Assets, Securities purchased under resale agreements	29	24
Net Amounts Presented in Balance Sheet, Securities purchased under resale agreements	29	24
Gross Amount Not Offset in Balance Sheet, Financial Instruments, Securities purchased under repurchase agreements	28	24
Net Amount, Securities purchased under repurchase agreements	1	0
Gross Amounts of Recognized Assets, Financial Assets	2,368	1,852
Gross Amounts Offset in Balance Sheet, Financial Assets	1,042	909
Net Amounts Presented in Balance Sheet, Financial Assets	1,326	943
Gross Amounts Not Offset In Balance Sheet, Financial Instruments, Financial Assets	83	84
Net Amount, Financial Assets	1,241	859
Financial Liabilities
Gross Amounts of Recognized Liabilities, Derivative liabilities	1,996	1,647
Gross Amounts Offset in Balance Sheet, Derivative liabilities	1,266	872
Net Amounts Presented in Balance Sheet, Derivative liabilities	730	775
Gross Amount Not Offset in Balance Sheet, Financial Instruments, Derivative liabilities	229	180
Derivative, Collateral, Obligation to Return Cash	1	0
Derivative, Collateral, Right to Reclaim Cash	2	0
Net Amount, Derivative liabilities	500	595
Gross Amounts of Recognized Liabilities, Securities sold under repurchase agreements	2	36
Net Amounts Presented in Balance Sheet, Securities sold under repurchase agreements	2	36
Gross Amount Not Offset in Balance Sheet, Financial Instruments, Securities sold under repurchase agreements	2	36
Gross Amounts of Recognized Liabilities, Financial Liabilities	1,998	1,683
Gross Amounts Offset in Balance Sheet, Financial Liabilities	1,266	872
Net Amounts Presented in Balance Sheet, Financial Liabilities	732	811
Gross Amount Not Offset in Balance Sheet, Financial Instruments, Financial Liabilities	231	216
Net Amount, Financial Liabilities	$ 500	$ 595