Long-Term Debt-Schedule (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term debt	$ 33,509	$ 27,524
HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	23,188	21,529
HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	10,321	5,995
Senior debt [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	21,168	19,799
Senior debt [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	5,771	1,265
Senior debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 11,412	8,224
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	2.75%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,747	5,196
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	6
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	1.70%
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 7,009	6,379
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	0.17%
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	2.91%
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	$ 165	259
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	0.43%
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	1.96%
Senior debt [Member] | FHLB Advances - Floating Rate [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	$ 5,600	1,000
Senior debt [Member] | FHLB Advances - Floating Rate [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, floating	0.67%
Senior debt [Member] | FHLB Advances - Floating Rate [Member] | HSBC Bank USA and its Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, floating	1.00%
Subordinated Debt [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,020	1,170
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1,170	1,170
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	9.30%
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	$ 4,458	4,638
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, fixed	4.86%
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%
Subordinated Debt [Member] | Floating Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 850	0
Interest rate, floating	2.61%
Junior Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	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%