Loans and asset quality- Allowance for Credit Losses Activity (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended						9 Months Ended
	Sep. 30, 2014		Jun. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 311		$ 326		$ 337		$ 344		$ 387
Charge-offs	(5)		(4)		(2)		(10)		(10)
Recoveries	1		1		2		3		3
Net (charge-offs) recoveries	(4)		(3)		0		(7)		(7)
Provision	(19)		(12)		2		(49)		(41)
Ending balance	288		311		339		288		339
Allowance for:
Loan losses	191		187		206		191		206
Lending-related commitments	97		124		133		97		133
Individually evaluated for impairment:
Loan balance	25		30		41		25		41
Allowance for loan losses	6		7		11		6		11
Collectively evaluated for impairment:
Loan balance	57,502		59,218		50,097		57,502		50,097
Allowance for loan losses	185		180		195		185		195
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	74		79		93		83		104
Charge-offs	(4)		0		(1)		(4)		(3)
Recoveries	0		1		0		1		0
Net (charge-offs) recoveries	(4)		1		(1)		(3)		(3)
Provision	1		(6)		(1)		(9)		(10)
Ending balance	71		74		91		71		91
Allowance for:
Loan losses	20		17		17		20		17
Lending-related commitments	51		57		74		51		74
Individually evaluated for impairment:
Loan balance	13		13		15		13		15
Allowance for loan losses	4		3		3		4		3
Collectively evaluated for impairment:
Loan balance	1,304		1,531		1,529		1,304		1,529
Allowance for loan losses	16		14		14		16		14
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	45		42		30		41		30
Charge-offs	0		0		0		0		0
Recoveries	0		0		0		0		0
Net (charge-offs) recoveries	0		0		0		0		0
Provision	2		3		2		6		2
Ending balance	47		45		32		47		32
Allowance for:
Loan losses	30		27		19		30		19
Lending-related commitments	17		18		13		17		13
Individually evaluated for impairment:
Loan balance	3		3		3		3		3
Allowance for loan losses	1		1		1		1		1
Collectively evaluated for impairment:
Loan balance	2,387		2,205		1,967		2,387		1,967
Allowance for loan losses	29		26		18		29		18
Financial institutions
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	43		48		34		49		36
Charge-offs	0		0		0		0		0
Recoveries	0		0		0		0		0
Net (charge-offs) recoveries	0		0		0		0		0
Provision	(18)		(5)		7		(24)		5
Ending balance	25		43		41		25		41
Allowance for:
Loan losses	9		8		7		9		7
Lending-related commitments	16		35		34		16		34
Individually evaluated for impairment:
Loan balance	0		0		1		0		1
Allowance for loan losses	0		0		0		0		0
Collectively evaluated for impairment:
Loan balance	5,465		5,761		3,724		5,465		3,724
Allowance for loan losses	9		8		7		9		7
Lease financings
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	33		35		41		37		49
Charge-offs	0		0		0		0		0
Recoveries	0		0		0		0		0
Net (charge-offs) recoveries	0		0		0		0		0
Provision	1		(2)		(2)		(3)		(10)
Ending balance	34		33		39		34		39
Allowance for:
Loan losses	34		33		39		34		39
Lending-related commitments	0		0		0		0		0
Individually evaluated for impairment:
Loan balance	0		0		0		0		0
Allowance for loan losses	0		0		0		0		0
Collectively evaluated for impairment:
Loan balance	1,293		1,321		1,278		1,293		1,278
Allowance for loan losses	34		33		39		34		39
Wealth management loans and mortgages
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	22		23		19		24		30
Charge-offs	0		(1)		0		(1)		0
Recoveries	0		0		0		0		0
Net (charge-offs) recoveries	0		(1)		0		(1)		0
Provision	0		0		(1)		(1)		(12)
Ending balance	22		22		18		22		18
Allowance for:
Loan losses	17		16		14		17		14
Lending-related commitments	5		6		4		5		4
Individually evaluated for impairment:
Loan balance	9		9		13		9		13
Allowance for loan losses	1		2		3		1		3
Collectively evaluated for impairment:
Loan balance	10,724		10,310		9,368		10,724		9,368
Allowance for loan losses	16		14		11		16		11
Other residential mortgages
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	47		50		75		54		88
Charge-offs	0		(1)		(1)		(2)		(7)
Recoveries	1		0		1		2		2
Net (charge-offs) recoveries	1		(1)		0		0		(5)
Provision	0		(2)		(5)		(6)		(13)
Ending balance	48		47		70		48		70
Allowance for:
Loan losses	48		47		70		48		70
Lending-related commitments	0		0		0		0		0
Individually evaluated for impairment:
Loan balance	0		0		0		0		0
Allowance for loan losses	0		0		0		0		0
Collectively evaluated for impairment:
Loan balance	1,262		1,309		1,433		1,262		1,433
Allowance for loan losses	48		47		70		48		70
All Other
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	0		0		0		0		2
Charge-offs	0		0		0		0		0
Recoveries	0		0		0		0		0
Net (charge-offs) recoveries	0		0		0		0		0
Provision	0		0		0		0		(2)
Ending balance	0		0		0		0		0
Allowance for:
Loan losses	0		0		0		0		0
Lending-related commitments	0		0		0		0		0
Individually evaluated for impairment:
Loan balance	0		0		0		0		0
Allowance for loan losses	0		0		0		0		0
Collectively evaluated for impairment:
Loan balance	19,638	[1]	20,275	[2]	17,334	[3]	19,638	[1]	17,334	[3]
Allowance for loan losses	0		0		0		0		0
Foreign
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	47		49		45		56		48
Charge-offs	(1)		(2)		0		(3)		0
Recoveries	0		0		1		0		1
Net (charge-offs) recoveries	(1)		(2)		1		(3)		1
Provision	(5)		0		2		(12)		(1)
Ending balance	41		47		48		41		48
Allowance for:
Loan losses	33		39		40		33		40
Lending-related commitments	8		8		8		8		8
Individually evaluated for impairment:
Loan balance	0		5		9		0		9
Allowance for loan losses	0		1		4		0		4
Collectively evaluated for impairment:
Loan balance	15,429		16,506		13,464		15,429		13,464
Allowance for loan losses	$ 33		$ 38		$ 36		$ 33		$ 36

[1] Includes $1,235 million of domestic overdrafts, $17,548 million of margin loans and $855 million of other loans at Sept. 30, 2014.

[2] Includes $1,748 million of domestic overdrafts, $17,685 million of margin loans and $842 million of other loans at June 30, 2014.

[3] Includes $1,487 million of domestic overdrafts, $15,146 million of margin loans and $701 million of other loans at Sept. 30, 2013.