Guarantee Arrangements and Pledged Assets (Details 4) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Outstanding repurchase demands received from GSEs and other third parties
GSEs	$ 122	$ 77
Others	45	25
Total	$ 167	$ 102

Outstanding repurchase demands received from government sponsored entities.

No definition available.

Name:	hsbcusa_OutstandingRepurchaseDemandsReceivedFromGovernmentSponsoredActivities
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant