Retained Earnings and Regulatory Capital Requirements - Capital Amounts and Ratios in Accordance With Current Banking Regulations (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
HSBC USA Inc [Member]
Total capital ratio:
Capital Amount	$ 21,017		$ 20,242
Well-Capitalized Minimum Ratio	10.00%	[1],[2]	10.00%	[3]
Actual Ratio, Total Capital	15.78%		16.36%	[3]
Tier 1 capital ratio:
Capital Amount, Tier 1 capital	15,205		14,409
Well-Capitalized Minimum Ratio, Tier 1 capital	6.00%	[1],[2]	6.00%	[1]
Actual Ratio, Tier 1 Capital	11.41%		11.65%	[3]
Common equity Tier 1 ratio:
Capital Amount, Common Equity Tier 1	13,754
Well Capitalized Minimum Ratio Common equity Tier 1	4.50%	[1],[2],[4]
Actual Ratio Common equity Tier 1	10.33%
Capital Amount, Common equity Tier 1 ratio			12,301
Well-Capitalized Minimum Ratio, Tier 1 common capital			5.00%	[1],[4],[5]
Actual Ratio, Tier 1 common capital			9.94%	[3],[4]
Tier 1 leverage ratio:
Capital Amount, Tier 1 leverage capital	15,205		14,409
Well-Capitalized Minimum Ratio, Tier 1 leverage capital	4.00%	[1],[2]	3.00%	[1],[6]
Actual Ratio, Tier 1 leverage capital	8.54%		7.90%	[3]
Risk weighted assets:
Risk Weighted Assets	133,211		123,737
HSBC Bank USA, National Association [Member]
Total capital ratio:
Capital Amount	22,760		21,324
Well-Capitalized Minimum Ratio	10.00%	[1],[2]	10.00%	[1]
Actual Ratio, Total Capital	17.86%		18.03%	[3]
Tier 1 capital ratio:
Capital Amount, Tier 1 capital	17,215		15,763
Well-Capitalized Minimum Ratio, Tier 1 capital	8.00%	[1],[2]	6.00%	[1]
Actual Ratio, Tier 1 Capital	13.51%		13.33%	[3]
Common equity Tier 1 ratio:
Capital Amount, Common Equity Tier 1	17,215
Well Capitalized Minimum Ratio Common equity Tier 1	6.50%	[1],[2],[4]
Actual Ratio Common equity Tier 1	13.51%
Capital Amount, Common equity Tier 1 ratio			15,763
Well-Capitalized Minimum Ratio, Tier 1 common capital			5.00%	[1],[4]
Actual Ratio, Tier 1 common capital			13.33%	[3],[4]
Tier 1 leverage ratio:
Capital Amount, Tier 1 leverage capital	17,215		15,763
Well-Capitalized Minimum Ratio, Tier 1 leverage capital	5.00%	[1],[2]	5.00%	[1]
Actual Ratio, Tier 1 leverage capital	10.06%		9.06%	[3]
Risk weighted assets:
Risk Weighted Assets	$ 127,456		$ 118,285

[1] HSBC USA and HSBC Bank USA are categorized as "well-capitalized," as defined by their principal regulators. To be categorized as well-capitalized under regulatory guidelines, a banking institution must have the minimum ratios reflected in the above table, and must not be subject to a directive, order, or written agreement to meet and maintain specific capital levels.

[2] As previously discussed, the minimum regulatory ratios for a depository institution to be well-capitalized will increase in 2015 under Basel III, and the new ratios are shown above. The total capital and Tier 1 capital ratios shown above for HSBC USA are the well-capitalized ratios for a bank holding company. There are no common equity Tier 1 or Tier 1 leverage ratio components in the definition of a well-capitalized bank holding company and the ratios shown are the required minimum ratios beginning in 2015.

[3] At December 31, 2013, capital ratios were reported according to Basel I rules and reflect the impact of the U.S. market risk final rule (known in the industry as Basel 2.5).

[4] Basel III introduces the common equity Tier 1 ratio. For December 31, 2013, the ratios presented are the Tier 1 common ratio calculated under Basel I.

[5] There was no Tier 1 common ratio component in the definition of a well-capitalized bank holding company under Basel I. The ratio shown is the required minimum Tier 1 common ratio, calculated under Basel I, as included in the Federal Reserve Board's final rule regarding capital plans for U.S. bank holding companies with total consolidated assets of $50 billion or more.

[6] There was no Tier 1 leverage ratio component in the definition of a well-capitalized bank holding company under Basel I. The ratio shown is the minimum required ratio.