Goodwill and other intangible assets - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Mortgage servicing rights activity [Abstract]
Fair value at the beginning of the period	$ 7,571	$ 8,347	$ 7,436	$ 9,614
MSR activity:
Originations of MSRs	147	148	447	518
Purchase of MSRs	(4)	3	435	9
Disposition of MSRs	0	11	(375)	(175)
Net additions	143	162	507	352
Changes due to collection/realization of expected cash flows	(233)	(216)	(677)	(702)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	(677)	(101)	(338)	(832)
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	(76)	44	(103)	33
Discount rates	0	0	(10)	(459)
Prepayment model changes and other	(12)	0	(99)	230
Total changes in valuation due to other inputs and assumptions	(88)	44	(212)	(196)
Total changes in valuation due to inputs and assumptions	(765)	(57)	(550)	(1,028)
Fair value at June 30	6,716	8,236	6,716	8,236
Change in unrealized gains/(losses) included in income related to MSRs	(765)	(57)	(550)	(1,028)
Contractual service fees, late fees and other ancillary fees included in income	634	701	1,945	2,189
Third-party mortgage loans serviced	706,000	771,000	706,000	771,000
Net servicer advances	6,600	8,600	6,600	8,600
MSR activity supplemental information
Commercial real estate, fair value period increase (decrease)	(1)	(1)	(3)	(5)
Commercial real estate, fair value	$ 7	$ 13	$ 7	$ 13