Goodwill and other intangible assets - Mortgage Servicing Rights (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Mortgage servicing rights activity [Abstract]
Fair value at the beginning of the period	$ 6,641,000,000	$ 8,552,000,000	$ 7,436,000,000	$ 9,614,000,000
MSR activity:
Originations of MSRs	145,000,000	178,000,000	300,000,000	370,000,000
Purchase of MSRs	438,000,000	3,000,000	439,000,000	6,000,000
Disposition of MSRs	(218,000,000)	2,000,000	(375,000,000)	(186,000,000)
Net additions	365,000,000	183,000,000	364,000,000	190,000,000
Changes due to collection/realization of expected cash flows	(229,000,000)	(239,000,000)	(444,000,000)	(486,000,000)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	816,000,000	(369,000,000)	339,000,000	(731,000,000)
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	(17,000,000)	0	(27,000,000)	(11,000,000)
Discount rates	0	(10,000,000)	(10,000,000)	(459,000,000)
Prepayment model changes and other	(5,000,000)	230,000,000	(87,000,000)	230,000,000
Total changes in valuation due to other inputs and assumptions	(22,000,000)	220,000,000	(124,000,000)	(240,000,000)
Total changes in valuation due to inputs and assumptions	794,000,000	(149,000,000)	215,000,000	(971,000,000)
Fair value at June 30	7,571,000,000	8,347,000,000	7,571,000,000	8,347,000,000
Change in unrealized gains/(losses) included in income related to MSRs held at June 30	794,000,000	(149,000,000)	215,000,000	(971,000,000)
Contractual service fees, late fees and other ancillary fees included in income	644,000,000	731,000,000	1,311,000,000	1,488,000,000
Third-party mortgage loans serviced at June 30	727,000,000,000	791,000,000,000	727,000,000,000	791,000,000,000
Net servicer advances at June 30	7,100,000,000	8,800,000,000	7,100,000,000	8,800,000,000
MSR activity supplemental information
Commercial real estate, fair value period increase (decrease)	0	(2,000,000)	(2,000,000)	(4,000,000)
Commercial real estate, fair value	$ 9,000,000	$ 14,000,000	$ 9,000,000	$ 14,000,000