Loans - Delinquency Ratio for Consumer Loan (Parenthetical) (Detail) (USD $) In Billions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Loans Receivable, Net [Abstract]
Residential mortgage loan delinquency carried at lower of amortized cost or fair value less cost to sell	$ 1.1	$ 1.0

Residential mortgage loan delinquency carried at lower of amortized cost or fair value less cost to sell.

No definition available.

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