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Financial Statements of HSBC USA Inc. (Parent) Statement of Comprehensive Income(Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 70us-gaap_NetIncomeLoss	$ 1us-gaap_NetIncomeLoss	$ 179us-gaap_NetIncomeLoss	$ 104us-gaap_NetIncomeLoss	$ (705)us-gaap_NetIncomeLoss	$ 4us-gaap_NetIncomeLoss	$ 180us-gaap_NetIncomeLoss	$ 183us-gaap_NetIncomeLoss	$ 354us-gaap_NetIncomeLoss	$ (338)us-gaap_NetIncomeLoss	$ (1,045)us-gaap_NetIncomeLoss
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Investment securities									176	(1,010)	109
Pension and post-retirement benefit plans									(5)	8	6
Total other comprehensive income (loss)									158	(877)	143
Comprehensive income (loss)									512us-gaap_ComprehensiveIncomeNetOfTax	(1,215)us-gaap_ComprehensiveIncomeNetOfTax	(902)us-gaap_ComprehensiveIncomeNetOfTax
HSBC USA Inc [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									354	(338)	(1,045)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Investment securities									176	(1,010)	109
Other-than-temporarily impaired debt securities held-to-maturity									60	7	0
Derivatives designated as cash flow hedges									(73)	118	28
Pension and post-retirement benefit plans									(5)	8	6
Total other comprehensive income (loss)									158	(877)	143
Comprehensive income (loss)									$ 512	$ (1,215)	$ (902)