Organization and Presentation Organization and Presentation (Details) $ in Millions	3 Months Ended
Sep. 30, 2016 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Out of period, income tax expense	$ 7

Income Tax Expense (Benefit), Out of Period Adjustment

No definition available.

Name:	hsbcusa_IncomeTaxExpenseBenefitOutofPeriodAdjustment
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration