Long-Term Debt-Schedule (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term debt	$ 37,739	$ 33,509
HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	23,378	23,188
Mark-to-market adjustment on fair value option debt	337	(62)
HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	14,361	10,321
Mark-to-market adjustment on fair value option debt	230	160
Senior debt [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	21,020	21,230
Senior debt [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	9,949	5,868
Senior debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 11,423	11,412
Interest rate, weighted average	2.20%
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	$ 1,748	2,747
Interest rate, weighted average	1.48%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC USA Inc [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, floating	1.24%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC USA Inc [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, floating	1.88%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	$ 4,031	6
Interest rate, weighted average	2.37%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, floating	0.74%
Senior debt [Member] | Floating Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, floating	2.62%
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 7,849	7,071
Interest rate, weighted average	1.75%
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, floating	0.85%
Senior debt [Member] | Structured Notes [Member] | HSBC USA Inc [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, floating	3.29%
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	$ 218	262
Interest rate, weighted average	1.25%
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, floating	0.92%
Senior debt [Member] | Structured Notes [Member] | HSBC Bank USA and its Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, floating	2.35%
Senior debt [Member] | FHLB Advances - Floating Rate [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	$ 5,700	5,600
Interest rate, weighted average	1.28%
Senior debt [Member] | FHLB Advances - Floating Rate [Member] | HSBC Bank USA and its Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate, floating	1.06%
Senior debt [Member] | FHLB Advances - Floating Rate [Member] | HSBC Bank USA and its Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate, floating	1.51%
Subordinated Debt [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,021	2,020
Subordinated Debt [Member] | Fixed Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1,171	1,170
Interest rate, weighted average	6.15%
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	$ 4,103	4,201
Interest rate, weighted average	5.86%
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%
Subordinated Debt [Member] | Floating Rate Notes [Member] | HSBC USA Inc [Member]
Debt Instrument [Line Items]
Long-term debt	$ 850	850
Interest rate, floating	3.13%
Interest rate, weighted average	3.13%
VIE-Issued Fixed Rate Notes [Member] | Fixed Rate Notes [Member] | HSBC Bank USA and its Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term debt	$ 79	$ 92
Interest rate, fixed	17.20%
Interest rate, weighted average	17.20%