Trading Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	$ 16,150	$ 16,850
Trading liabilities	4,879	4,908
U.S. Treasury [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	3,391	3,560
US Government agency issued or guaranteed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	122	24
US Government sponsored enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	210	222
Asset backed securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	236	365
Corporate and foreign bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	6,180	6,481
Other securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	12	15
Precious metals [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	2,274	1,772
Trading liabilities	524	62
Securities sold, not yet purchased [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading liabilities	1,722	1,060
Derivatives [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	3,725	4,411
Derivatives [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading liabilities	$ 2,633	$ 3,786