Consolidated Statement of Income (Unaudited) (Parenthetical) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Income Statement [Abstract]
OTTI losses in non-credit component on securities	$ 0	$ 0	$ 0	$ 0
OTTI on securities available-for-sale and held to maturity	$ 0	$ 13	$ 0	$ 41

Name:

hsbcusa_OttiOnSecuritiesAvailableForSaleAndHeldToMaturity

Namespace Prefix:

hsbcusa

Data Type:

xbrli:monetaryItemType

Balance Type:

debit

Period Type:

duration