Securities Financing Agreements (Offsetting Financing Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivative assets
Gross Amounts of Recognized Assets/Liabilities	$ 871	$ 1,322
Gross Amounts Offset in Balance Sheet	354	607
Net Amounts Presented in Balance Sheet	517	715
Gross Amounts Not Offset In Balance Sheet, Financial Instruments	14	25
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	503	690
Securities borrowed or purchased under resale agreements
Gross Amounts of Recognized Assets/Liabilities	33,974	31,845
Gross Amounts Offset in Balance Sheet	11,606	10,951
Net Amounts Presented in Balance Sheet	22,368	20,894
Gross Amounts Not Offset in Balance Sheet, Financial Instruments	22,291	20,816
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	77	78
Total Financial Assets
Gross Amounts of Recognized Assets/Liabilities	34,845	33,167
Gross Amounts Offset in Balance Sheet	11,960	11,558
Net Amounts Presented in Balance Sheet	22,885	21,609
Gross Amounts Not Offset In Balance Sheet, Financial Instruments	22,305	20,841
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	580	768
Derivative liabilities
Gross Amounts of Recognized Assets/Liabilities	804	1,127
Gross Amounts Offset in Balance Sheet	322	620
Net Amounts Presented in Balance Sheet	482	507
Gross Amount Not Offset in Balance Sheet, Financial Instruments	69	142
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	413	365
Securities loaned or sold under repurchase agreements
Gross Amounts of Recognized Assets/Liabilities	38,891	37,388
Gross Amounts Offset in Balance Sheet	11,606	10,951
Net Amounts Presented in Balance Sheet	27,285	26,437
Gross Amounts Not Offset in Balance Sheet, Financial Instruments	26,434	25,639
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	851	798
Total Financial Liabilities
Gross Amounts of Recognized Assets/Liabilities	39,695	38,515
Gross Amounts Offset in Balance Sheet	11,928	11,571
Net Amounts Presented in Balance Sheet	27,767	26,944
Gross Amount Not Offset in Balance Sheet, Financial Instruments	26,503	25,781
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	$ 1,264	$ 1,163