Guarantee Arrangements and Pledged Assets - Additional Information (Detail) (USD $)	3 Months Ended			36 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2007 HSBC Securities [Member]	Mar. 31, 2013 Available-for-sale Securities [Member]	Dec. 31, 2012 Available-for-sale Securities [Member]	Mar. 31, 2013 Financial Guarantee [Member] Collateralized Securities [Member]	Mar. 31, 2013 Trading Assets [Member]	Dec. 31, 2012 Trading Assets [Member]
Guarantor Obligations [Line Items]
Outstanding financial standby letters of credit	$ 5,400,000,000	$ 5,600,000,000
Outstanding financial standby performance guarantees	2,700,000,000	2,900,000,000
Deferred fee on stand by letters of credit	45,000,000	46,000,000
Allowance for credit losses on unfunded standby letters of credit	18,000,000	19,000,000
Minimum time to resolve case	3 months
Maximum time to resolve case	12 months
Principal amount outstanding on loans sold to government sponsored entities	14,200,000,000	15,100,000,000
Principal amount outstanding on loans from our legacy broker channel	9,100,000,000	9,600,000,000
Estimated mortgage repurchase liability	211,000,000		223,000,000
Range of possible losses in excess of recorded repurchase liability, minimum							0
Range of possible losses in excess of recorded repurchase liability, maximum							205,000,000
Liquidity facilities	2,500,000,000	2,200,000,000
Securities available-for-sale					6,600,000,000	6,500,000,000
Fair Value of Securities Received as Collateral that Can be Resold or Repledged								2,500,000,000	2,200,000,000
Separately reported available-for-sale pledged assets	12,800,000,000	5,700,000,000
Securities sold under agreements to repurchase	1,300,000,000	1,300,000,000
Related Party, Whole Loan Securitization Program, Amounts of Transaction				$ 24,000,000,000