Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses and Related Loan Balance by Product (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 606		$ 647
Provision (credit) for credit losses	16	[1]	21	[1]
Charge-offs	(67)		(110)
Recoveries	19		10
Net (charge offs) recoveries	(48)		(100)
Balance at end of period	574		568
Ending balance: collectively evaluated for impairment	497		448
Ending balance: individually evaluated for impairment	77		120
Total allowances for credit losses	574		568
Collectively evaluated for impairment	66,754		60,598
Individually evaluated for impairment	527	[2]	782	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	1,616		1,552
Total loans	68,897		62,932		67,695
Commercial Loan [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Total loans	49,893				48,494
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	108		162
Provision (credit) for credit losses	2		9
Charge-offs	(19)		(58)
Recoveries	2		3
Net (charge offs) recoveries	(17)		(55)
Balance at end of period	93		116
Ending balance: collectively evaluated for impairment	84		89
Ending balance: individually evaluated for impairment	9		27
Total allowances for credit losses	93		116
Collectively evaluated for impairment	8,905		7,926
Individually evaluated for impairment	260	[2]	393	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	0		0
Total loans	9,165		8,319		9,034
Commercial Loan [Member] | Business and Corporate Banking [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	112		97
Provision (credit) for credit losses	19		2
Charge-offs	(5)		(6)
Recoveries	3		3
Net (charge offs) recoveries	(2)		(3)
Balance at end of period	129		96
Ending balance: collectively evaluated for impairment	126		88
Ending balance: individually evaluated for impairment	3		8
Total allowances for credit losses	129		96
Collectively evaluated for impairment	15,681		12,678
Individually evaluated for impairment	17	[2]	47	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	0		0
Total loans	15,698		12,725		14,446
Commercial Loan [Member] | Global Banking [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	68		41
Provision (credit) for credit losses	7		(1)
Charge-offs	(8)		0
Recoveries	0		0
Net (charge offs) recoveries	(8)		0
Balance at end of period	67		40
Ending balance: collectively evaluated for impairment	67		40
Ending balance: individually evaluated for impairment	0		0
Total allowances for credit losses	67		40
Collectively evaluated for impairment	21,979		19,700
Individually evaluated for impairment	0	[2]	18	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	0		0
Total loans	21,979		19,718		21,625
Commercial Loan [Member] | Other Commercial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	20		17
Provision (credit) for credit losses	(4)		0
Charge-offs	0		0
Recoveries	3		0
Net (charge offs) recoveries	3		0
Balance at end of period	19		17
Ending balance: collectively evaluated for impairment	18		17
Ending balance: individually evaluated for impairment	1		0
Total allowances for credit losses	19		17
Collectively evaluated for impairment	3,031		2,803
Individually evaluated for impairment	20	[2]	74	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	0		0
Total loans	3,051		2,877		3,389
Consumer Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period					77
Balance at end of period	59				77
Total allowances for credit losses	59				77
Total loans	19,004				19,201
Consumer Loans [Member] | Residential Mortgages [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	186		210
Provision (credit) for credit losses	(16)		(3)
Charge-offs	(17)		(16)
Recoveries	3		1
Net (charge offs) recoveries	(14)		(15)
Balance at end of period	156		192
Ending balance: collectively evaluated for impairment	96		115
Ending balance: individually evaluated for impairment	60		77
Total allowances for credit losses	156		192
Collectively evaluated for impairment	14,082		13,962
Individually evaluated for impairment	202	[2]	216	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	1,616		1,552
Total loans	15,900		15,730		15,826
Consumer Loans [Member] | Home Equity Mortgages [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	49		45
Provision (credit) for credit losses	2		17
Charge-offs	(5)		(12)
Recoveries	6		0
Net (charge offs) recoveries	1		(12)
Balance at end of period	52		50
Ending balance: collectively evaluated for impairment	50		47
Ending balance: individually evaluated for impairment	2		3
Total allowances for credit losses	52		50
Collectively evaluated for impairment	1,919		2,215
Individually evaluated for impairment	19	[2]	21	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	0		0
Total loans	1,938		2,236		2,011
Consumer Loans [Member] | Credit Card [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	50		55
Provision (credit) for credit losses	5		(2)
Charge-offs	(11)		(12)
Recoveries	1		1
Net (charge offs) recoveries	(10)		(11)
Balance at end of period	45		42
Ending balance: collectively evaluated for impairment	43		37
Ending balance: individually evaluated for impairment	2		5
Total allowances for credit losses	45		42
Collectively evaluated for impairment	674		736
Individually evaluated for impairment	9	[2]	13	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	0		0
Total loans	683		749		854
Consumer Loans [Member] | Other consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	13		20
Provision (credit) for credit losses	1		(1)
Charge-offs	(2)		(6)
Recoveries	1		2
Net (charge offs) recoveries	(1)		(4)
Balance at end of period	13		15
Ending balance: collectively evaluated for impairment	13		15
Ending balance: individually evaluated for impairment	0		0
Total allowances for credit losses	13		15
Collectively evaluated for impairment	483		578
Individually evaluated for impairment	0	[2]	0	[2]
Loans carried at the lower of amortized cost or fair value less cost to sell	0		0
Total loans	$ 483		$ 578		$ 510

[1] The provision assigned to the segments is based on the segments' net charge offs and the change in allowance for credit losses.

[2] For consumer loans, these amounts represent TDR Loans for which we evaluate reserves using a discounted cash flow methodology. Each loan is individually identified as a TDR Loan and then grouped together with other TDR Loans with similar characteristics. The discounted cash flow analysis is then applied to these groups of TDR Loans. Loans individually evaluated for impairment exclude TDR loans that are carried at the lower of amortized cost or fair value of the collateral less cost to sell which totaled $718 million and $632 million at March 31, 2014 and 2013, respectively.