Pension and Other Postretirement Benefits Pension and Other Postretirement Benefits-Assumptions (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.35%	4.25%	4.95%
Salary increase assumption	2.75%	2.75%	2.75%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.25%	4.95%	5.20%
Salary increase assumption	2.75%	2.75%	2.90%
HSBC North America [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.60%	5.30%	5.60%
Salary increase assumption	2.75%	2.75%	2.90%
Expected long-term rate of return on Plan assets	7.00%	7.25%	7.70%