Guarantee Arrangements and Pledged Assets - Outstanding Repurchase Demands Received From GSEs and Other Third Parties (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Outstanding repurchase demands on loans sourced from our legacy broker channel	$ 64	$ 65

Outstanding repurchase demands on loans sourced from our legacy broker channel.

No definition available.

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