Intangible Assets - Residential Mortgage Loans Serviced for Others (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Outstanding principal balances at period end	$ 31,039	$ 32,041
Custodial balances maintained and included in noninterest bearing deposits at period end	$ 722	$ 810

Custodial balances maintained and included in noninterest bearing deposits at period end.

No definition available.

Name:	husi_CustodialBalancesMaintainedAndIncludedInNoninterestBearingDepositsAtPeriodEnd
Namespace Prefix:	husi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant