Long-Term Debt-Schedule (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term debt	$ 27,524	$ 22,847
HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	21,529	16,049
HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	5,995	6,798
Senior debt [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	19,799	14,170
Senior debt [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	1,265	1,345
Senior debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	8,224	4,497
Senior debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	1.30%
Senior debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	3.50%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	5,196	4,249
Senior debt [Member] | Floating Rate Notes [Member] | HSBC USA Inc [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, floating	0.50%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC USA Inc [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, floating	1.59%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	6	12
Senior debt [Member] | Floating Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, floating	0.15%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, floating	2.03%
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	6,379	5,424
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	0.00%
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	2.56%
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	259	294
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	0.00%
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	2.31%
Senior debt [Member] | FHLB Advances - Floating Rate [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	1,000	1,000
Interest rate, floating	0.32%
Senior debt [Member] | Other [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	0	39
Interest rate, fixed	0.00%
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	1,170	1,319
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	5.00%
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	9.50%
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	4,638	5,361
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	4.88%
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	7.00%
Junior Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	560	560
Junior Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	7.75%
Junior Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	8.38%
VIE-Issued Fixed Rate Notes [Member] | Fixed Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	$ 92	$ 92
Interest rate, fixed	17.20%