Accumulated Other Comprehensive Income/(Loss) - Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 247,573
Net change	436	$ 241
Ending balance	250,157	235,864
Accumulated other comprehensive income (loss) - supplemental information
Net pre-tax unrealized gains (losses) in AOCI on securities on the date of transfer				$ (9)
Unrealized gains/(losses) on investment securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	2,629	4,773
Cumulative effect of change in accounting principle			$ 0
Net change	425	89
Ending balance	3,054	4,862
Translation adjustments, net of hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(162)	(147)
Cumulative effect of change in accounting principle			0
Net change	(2)	(10)
Ending balance	(164)	(157)
Cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(44)	(95)
Cumulative effect of change in accounting principle			0
Net change	(70)	77
Ending balance	(114)	(18)
Defined benefit pension and OPEB plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(2,231)	(2,342)
Cumulative effect of change in accounting principle			0
Net change	25	85
Ending balance	(2,206)	(2,257)
DVA on fair value option elected liabilities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Cumulative effect of change in accounting principle			154
Net change	58
Ending balance	212
Accumulated other comprehensive income/(loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	192	2,189
Cumulative effect of change in accounting principle			$ 154
Net change	436	241
Ending balance	$ 782	$ 2,430