Guarantee Arrangements, Pledged Assets and Repurchase Agreements - Carrying Value and Contractual Amounts of our Sell Protection Credit Derivatives and Major Off-Balance Sheet Guarantee Arrangements (Detail) - USD ($) $ in Millions		Dec. 31, 2019		Dec. 31, 2018
Guarantor Obligations [Line Items]
Carrying Value		$ (63)		$ (562)
Notional/maximum exposure to loss		48,175	[1]	54,356
Credit derivatives [Member]
Guarantor Obligations [Line Items]
Carrying Value	[2],[3]	(63)		(562)
Notional/maximum exposure to loss	[2],[3]	38,739		45,384
Financial standby letters of credit, net of participations [Member]
Guarantor Obligations [Line Items]
Carrying Value	[4],[5]	0		0
Notional/maximum exposure to loss	[4],[5]	5,657		5,302
Performance standby letters of credit, net of participations [Member]
Guarantor Obligations [Line Items]
Carrying Value	[4],[5]	0		0
Notional/maximum exposure to loss	[4],[5]	3,779		3,670
Affiliated Entity [Member] | Credit derivatives [Member]
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss		18,391		25,734
Affiliated Entity [Member] | Financial and performance standby letters of credit [Member]
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss		$ 1,623		$ 1,321

[1] External ratings for most of the obligors are not available. Presented above are the internal credit ratings which are developed using similar methodologies and rating scale equivalent to external credit ratings for purposes of classification as investment grade and non-investment grade.

[2] For credit derivatives, the maximum loss is represented by the notional amounts without consideration of mitigating effects from collateral or recourse arrangements.

[3] Includes $18,391 million and $25,734 million of notional issued for the benefit of HSBC affiliates at December 31, 2019 and 2018, respectively.

[4] For standby letters of credit, maximum loss represents losses to be recognized assuming the letters of credit have been fully drawn and the obligors have defaulted with zero recovery.

[5] Includes $1,623 million and $1,321 million of both financial and performance standby letters of credit issued for the benefit of HSBC affiliates at December 31, 2019 and 2018, respectively.