Pensions and Other Postretirement Benefits-Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 meeting review	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Leveraged Loans, Redemption Fee, Percent	5.00%
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Leveraged Loans Under Redemption Fee Restriction	$ 39
Postretirement Plans Other Than Pensions [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected benefit payments, in next fiscal year	5
Funded status of plan, asset (liablity)	(62)
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health care cost trend rate assumed for current fiscal year, participants under 65	7.00%
Health care cost trend rate assumed for current fiscal year, participants over 65	6.70%
Ultimate health care cost trend rate	4.50%
Year that rate reaches ultimate trend rate	2027
Hsbc North America [Member] | HSBC North America Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Duration used to calculate average returns for portfolio	20 years
Number of quarterly meetings to manage the pension plan's investment strategy (meeting)	4
Number of strategic reviews to manage the pension plan's investment strategy (review)	2
Number of in-depth manager performance reviews to manage the pension plan's investment strategy (review)	2
Long-term performance objectives, expected rate of return on plan assets	6.00%
Target asset allocations	100.00%
Increase (decrease) in fair value of plan assets, percent	12.80%
Contributions by employer	74	131
Adjusted funding target attainment percentage	90.00%
Present value of benefits earned by plan participants on annual basis	3,127
Expected benefit payments, in next fiscal year	$ 169
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocations	40.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Standard & Poor's 500 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	9.50%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Russell 2000 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	3.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | EAFE [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	8.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Standard & Poor's Dev ex-US Small Cap [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	3.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | MSCI AC World Free Index [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	7.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | MSCI Emerging Markets [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	5.50%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | High Yield/Emerging Market Debt/Leveraged Loans Blended Benchmark [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	4.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocations	59.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Barclays Long Government or Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	59.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocations	1.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | U.S. Treasury [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Long-term Performance Objectives, Blended Index, Percentage	1.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Investments for Long-term Growth [Member] | Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocations	95.00%
Hsbc North America [Member] | HSBC North America Pension Plan [Member] | Near-term Investments [Member] | Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocations	5.00%