Segment Information (Operating Income of Reportable Segments) (Reconciling Items) (Details) - Segment Reconciling Items - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Terminated hedges of foreign currency earnings	$ 7	$ 79	$ 43	$ 160
Current period yield adjustments	113	125	240	248
Principal source of earnings	17	24	27	48
Other trading account assets	(34)	26	(56)	(32)
Foreign currency exchange movements	(217)	133	(538)	158
Other activities	$ 2	$ (2)	$ 12	$ 1