Retained Earnings and Regulatory Capital Requirements - Capital Amounts and Ratios in Accordance With Current Banking Regulations (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
HSBC USA Inc [Member]
Total capital ratio:
Capital Amount	$ 20,639		$ 20,242
Well-Capitalized Minimum Ratio, Total capital			10.00%	[1]
Actual Ratio, Total Capital	16.05%		16.36%
Tier 1 capital ratio:
Capital Amount, Tier 1 capital	14,964		14,409
Well-Capitalized Minimum Ratio, Tier 1 capital			6.00%	[1]
Actual Ratio, Tier 1 Capital	11.63%		11.65%
Common equity Tier 1 ratio:
Capital Amount, Common equity Tier 1 ratio			12,301
Capital Amount, Common Equity Tier One, Basel III.	13,486
Well-Capitalized Minimum Ratio, Tier 1 common capital			5.00%	[2],[3]
Actual Ratio Common Equity Tier 1	10.48%
Actual Ratio, Tier 1 common capital			9.94%	[1]
Tier 1 leverage ratio:
Capital Amount, Tier 1 leverage capital	14,964		14,409
Well-Capitalized Minimum Ratio, Tier 1 leverage capital			3.00%	[1],[4]
Actual Ratio, Tier 1 leverage capital	8.16%		7.90%
Risk weighted assets:
Risk Weighted Assets	128,633		123,737
HSBC Bank USA, National Association [Member]
Total capital ratio:
Capital Amount	22,267		21,324
Well-Capitalized Minimum Ratio, Total capital	10.00%	[5]	10.00%	[1]
Actual Ratio, Total Capital	18.18%		18.03%
Tier 1 capital ratio:
Capital Amount, Tier 1 capital	16,732		15,763
Well-Capitalized Minimum Ratio, Tier 1 capital	8.00%	[5]	6.00%	[1]
Actual Ratio, Tier 1 Capital	13.66%		13.33%
Well Capitalized Minimum Ratio Common Equity Tier 1	6.50%	[2],[5]
Common equity Tier 1 ratio:
Capital Amount, Common equity Tier 1 ratio			15,763
Capital Amount, Common Equity Tier One, Basel III.	16,732
Well-Capitalized Minimum Ratio, Tier 1 common capital			5.00%	[2]
Actual Ratio Common Equity Tier 1	13.66%
Actual Ratio, Tier 1 common capital			13.33%
Tier 1 leverage ratio:
Capital Amount, Tier 1 leverage capital	16,732		15,763
Well-Capitalized Minimum Ratio, Tier 1 leverage capital	5.00%	[5]	5.00%
Actual Ratio, Tier 1 leverage capital	9.49%		9.06%
Risk weighted assets:
Risk Weighted Assets	$ 122,505		$ 118,285

[1] 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).

[2] 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.

[3] 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.

[4] 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.

[5] HSBC Bank USA is categorized as "well-capitalized," as defined by its 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. 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. There is no definition of a well-capitalized bank holding company under Basel III