Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses and Related Loan Balance by Product (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period					$ 912				$ 680	$ 912		$ 680	$ 606
Provision charged (credited) to income		$ 19	$ 62	$ 134	157	$ 267	$ 47	$ (6)	53	372	[1]	361	188
Charge offs										(309)	[1],[2]	(167)	(169)
Recoveries										42		38	55
Net (charge offs) recoveries										(267)		(129)	(114)
Balance at end of period		1,017				912				1,017		912	680
Ending balance: collectively evaluated for impairment														$ 698		$ 823		$ 603
Ending balance: individually evaluated for impairment														319		89		77
Total allowances for credit losses		1,017			912	912			680	912		680	606	1,017		912		680
Collectively evaluated for impairment	[3]													71,728		80,736		75,630
Individually evaluated for impairment	[4]													1,121		660		530
Loans carried at the lower of amortized cost or fair value less cost to sell														1,026		1,521		1,581
Total loans														73,875		82,917		77,741
Commercial Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Total loans														54,216		62,453
Commercial Loans [Member] | Construction and Other Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period					86				89	86		89	108
Provision charged (credited) to income										0	[1]	2	2
Charge offs										(1)	[1],[2]	(10)	(24)
Recoveries										7		5	3
Net (charge offs) recoveries										6		(5)	(21)
Balance at end of period		92				86				92		86	89
Ending balance: collectively evaluated for impairment														91		85		84
Ending balance: individually evaluated for impairment														1		1		5
Total allowances for credit losses		92			86	86			89	86		89	108	92		86		89
Collectively evaluated for impairment	[3]													10,847		9,890		10,103
Individually evaluated for impairment	[4]													43		110		197
Loans carried at the lower of amortized cost or fair value less cost to sell														0		0		0
Total loans														10,890		10,000		10,300
Commercial Loans [Member] | Business and Corporate Banking [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	[5]				407				251	407		251	105
Provision charged (credited) to income	[5]									10	[1]	215	157
Charge offs	[5]									(110)	[1],[2]	(69)	(19)
Recoveries	[5]									10		10	8
Net (charge offs) recoveries	[5]									(100)		(59)	(11)
Balance at end of period	[5]	317				407				317		407	251
Ending balance: collectively evaluated for impairment	[5]													262		355		227
Ending balance: individually evaluated for impairment	[5]													55		52		24
Total allowances for credit losses	[5]	317			407	407			251	407		251	105	317		407		251
Collectively evaluated for impairment	[3],[5]													13,738		14,148		13,788
Individually evaluated for impairment	[4],[5]													342		217		90
Loans carried at the lower of amortized cost or fair value less cost to sell	[5]													0		0		0
Total loans	[5]													14,080		14,365		13,878
Commercial Loans [Member] | Global Banking [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	[5]				267				131	267		131	75
Provision charged (credited) to income	[5]									348	[1]	136	64
Charge offs	[5]									(107)	[1],[2]	0	(8)
Recoveries	[5]									0		0	0
Net (charge offs) recoveries	[5]									(107)		0	(8)
Balance at end of period	[5]	508				267				508		267	131
Ending balance: collectively evaluated for impairment	[5]													257		267		131
Ending balance: individually evaluated for impairment	[5]													251		0		0
Total allowances for credit losses	[5]	508			267	267			131	267		131	75	508		267		131
Collectively evaluated for impairment	[3],[5]													26,094		34,601		30,328
Individually evaluated for impairment	[4],[5]													661		119		0
Loans carried at the lower of amortized cost or fair value less cost to sell	[5]													0		0		0
Total loans	[5]													26,755	[6]	34,720	[6]	30,328
Commercial Loans [Member] | Other Commercial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period					19				21	19		21	20
Provision charged (credited) to income										(6)	[1]	(2)	(7)
Charge offs										0	[1],[2]	(1)	(1)
Recoveries										0		1	9
Net (charge offs) recoveries										0		0	8
Balance at end of period		13				19				13		19	21
Ending balance: collectively evaluated for impairment														12		18		20
Ending balance: individually evaluated for impairment														1		1		1
Total allowances for credit losses		13			19	19			21	19		21	20	13		19		21
Collectively evaluated for impairment	[3]													2,484		3,361		3,573
Individually evaluated for impairment	[4]													7		7		8
Loans carried at the lower of amortized cost or fair value less cost to sell														0		0		0
Total loans														2,491		3,368		3,581
Consumer Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Total loans														19,659		20,464
Consumer Loans [Member] | Residential Mortgages [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period					68				107	68		107	186
Provision charged (credited) to income										(9)	[1]	(15)	(40)
Charge offs										(45)	[1],[2]	(35)	(55)
Recoveries										12		11	16
Net (charge offs) recoveries										(33)		(24)	(39)
Balance at end of period		26				68				26		68	107
Ending balance: collectively evaluated for impairment														17		35		64
Ending balance: individually evaluated for impairment														9		33		43
Total allowances for credit losses		26			68	68			107	68		107	186	26		68		107
Collectively evaluated for impairment	[3]													16,165		16,112		14,926
Individually evaluated for impairment	[4]													60		197		224
Loans carried at the lower of amortized cost or fair value less cost to sell														956		1,449		1,511
Total loans														17,181	[7],[8]	17,758		16,661
Consumer Loans [Member] | Home Equity Mortgages [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period					24				32	24		32	49
Provision charged (credited) to income										(1)	[1]	(4)	(14)
Charge offs										(8)	[1],[2]	(8)	(13)
Recoveries										5		4	10
Net (charge offs) recoveries										(3)		(4)	(3)
Balance at end of period		20				24				20		24	32
Ending balance: collectively evaluated for impairment														19		23		30
Ending balance: individually evaluated for impairment														1		1		2
Total allowances for credit losses		20			24	24			32	24		32	49	20		24		32
Collectively evaluated for impairment	[3]													1,335		1,523		1,709
Individually evaluated for impairment	[4]													3		5		5
Loans carried at the lower of amortized cost or fair value less cost to sell														70		72		70
Total loans														1,408	[9]	1,600		1,784
Consumer Loans [Member] | Credit Cards [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period					32				39	32		39	50
Provision charged (credited) to income										26	[1]	20	23
Charge offs										(30)	[1],[2]	(32)	(41)
Recoveries										6		5	7
Net (charge offs) recoveries										(24)		(27)	(34)
Balance at end of period		34				32				34		32	39
Ending balance: collectively evaluated for impairment														33		31		37
Ending balance: individually evaluated for impairment														1		1		2
Total allowances for credit losses		34			32	32			39	32		39	50	34		32		39
Collectively evaluated for impairment	[3]													683		694		714
Individually evaluated for impairment	[4]													5		5		6
Loans carried at the lower of amortized cost or fair value less cost to sell														0		0		0
Total loans														688	[10]	699		720
Consumer Loans [Member] | Other consumer [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period					9				10	9		10	13
Provision charged (credited) to income										4	[1]	9	3
Charge offs										(8)	[1],[2]	(12)	(8)
Recoveries										2		2	2
Net (charge offs) recoveries										(6)		(10)	(6)
Balance at end of period		7				9				7		9	10
Ending balance: collectively evaluated for impairment														7		9		10
Ending balance: individually evaluated for impairment														0		0		0
Total allowances for credit losses		$ 7			$ 9	$ 9			$ 10	$ 9		$ 10	$ 13	7		9		10
Collectively evaluated for impairment	[3]													382		407		489
Individually evaluated for impairment	[4]													0		0		0
Loans carried at the lower of amortized cost or fair value less cost to sell														0		0		0
Total loans														$ 382		$ 407		$ 489

[1] The provision for credit losses and charge-offs for residential mortgage loans during 2016 includes $11 million related to the lower of amortized cost or fair value adjustment attributable to credit factors for loans transferred to held for sale. See Note 7, "Loans Held for Sale," for additional information.

[2] For collateral dependent loans that are transferred to held for sale, the existing allowance for credit losses at the time of transfer are recognized as a charge-off. We transferred to held for sale certain residential mortgage loans during 2016 and, accordingly, we recognized the existing allowance for credit losses on these loans as additional charge-offs totaling $22 million during 2016.

[3] Global banking includes loans to HSBC affiliates totaling $3,274 million, $4,815 million and 4,821 million at December 31, 2016, 2015 and 2014, respectively, for which we do not carry an associated allowance for credit losses.

[4] For consumer loans and certain small business 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 $672 million, $881 million and $763 million at December 31, 2016, 2015 and 2014, respectively.

[5] During the fourth quarter of 2016, we transferred certain customer relationships from CMB to GB&M as discussed further in Note 22, "Business Segments," in the accompanying consolidated financial statements. As a result, we reclassified $4.8 billion, $3.9 billion and $3.4 billion of loans and $27 million, $24 million and $7 million of allowance for credit losses from business and corporate banking to global banking at December 31, 2015, 2014 and 2013, respectively, to conform with the current year presentation.

[6] Represents large multinational firms including globally focused U.S. corporate and financial institutions, U.S. dollar lending to multinational banking customers managed by HSBC on a global basis and complex large business customers supported by GB&M relationship managers. Also includes loans to HSBC affiliates which totaled $3,274 million and $4,815 million at December 31, 2016 and 2015, respectively. See Note 21, "Related Party Transactions," for additional information regarding loans to HSBC affiliates.

[7] The decrease in nonaccrual loans at December 31, 2016 reflects the impact of transfers of certain residential mortgage loans to held for sale during 2016.

[8] The decrease in past due loans at December 31, 2016 reflects the impact of transfers of certain residential mortgage loans to held for sale during 2016. See Note 7, "Loans Held for Sale" for additional details.

[9] Home equity mortgage maturities reflect estimates based on historical payment patterns.

[10] As credit card receivables do not have stated maturities, the table reflects estimates based on historical payment patterns.