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		Dec. 31, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss		$ 51,036	$ 66,721
Credit derivatives [Member]
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss	[1],[2]	42,328	58,329
Affiliated Entity [Member] | Credit derivatives [Member]
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss		25,639	29,999
Affiliated Entity [Member] | Financial and performance standby letters of credit [Member]
Guarantor Obligations [Line Items]
Notional/maximum exposure to loss		$ 1,264	$ 1,315

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

[2] Includes $25,639 million and $29,999 million of notional issued for the benefit of HSBC affiliates at December 31, 2017 and 2016, respectively.