Securities Financing Arrangements (Offsetting Financing Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivative assets
Gross Amounts of Recognized Assets/Liabilities	$ 1,626	$ 1,839
Gross Amounts Offset in Balance Sheet	770	909
Net Amounts Presented in Balance Sheet	856	930
Gross Amounts Not Offset In Balance Sheet, Financial Instruments	20	67
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	836	863
Securities borrowed or purchased under resale agreements
Gross Amounts of Recognized Assets/Liabilities	31,386	36,521
Gross Amounts Offset in Balance Sheet	11,639	5,449
Net Amounts Presented in Balance Sheet	19,747	31,072
Gross Amounts Not Offset in Balance Sheet, Financial Instruments	19,657	30,946
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	90	126
Total Financial Assets
Gross Amounts of Recognized Assets/Liabilities	33,012	38,360
Gross Amounts Offset in Balance Sheet	12,409	6,358
Net Amounts Presented in Balance Sheet	20,603	32,002
Gross Amounts Not Offset In Balance Sheet, Financial Instruments	19,677	31,013
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	926	989
Derivative liabilities
Gross Amounts of Recognized Assets/Liabilities	1,684	1,649
Gross Amounts Offset in Balance Sheet	1,047	872
Net Amounts Presented in Balance Sheet	637	777
Gross Amount Not Offset in Balance Sheet, Financial Instruments	176	179
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	5	0
Net Amount	456	598
Securities loaned or sold under repurchase agreements
Gross Amounts of Recognized Assets/Liabilities	36,255	34,590
Gross Amounts Offset in Balance Sheet	11,639	5,449
Net Amounts Presented in Balance Sheet	24,616	29,141
Gross Amounts Not Offset in Balance Sheet, Financial Instruments	23,812	28,360
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	0	0
Net Amount	804	781
Total Financial Liabilities
Gross Amounts of Recognized Assets/Liabilities	37,939	36,239
Gross Amounts Offset in Balance Sheet	12,686	6,321
Net Amounts Presented in Balance Sheet	25,253	29,918
Gross Amount Not Offset in Balance Sheet, Financial Instruments	23,988	28,539
Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received/Pledged	5	0
Net Amount	$ 1,260	$ 1,379