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 - Additional Information (Detail) - USD ($) $ in Millions		Jun. 30, 2018		Dec. 31, 2017
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss		$ 51,628	[1]	$ 51,036
Credit derivatives [Member]
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss	[2],[3]	42,543		42,328
Affiliated Entity [Member] | Credit derivatives [Member]
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss		23,033		25,639
Affiliated Entity [Member] | Financial and performance standby letters of credit [Member]
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss		$ 1,194		$ 1,264

[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 $23,033 million and $25,639 million of notional issued for the benefit of HSBC affiliates at June 30, 2018 and December 31, 2017, respectively.