Guarantee Arrangements and Pledged Assets and Collateral - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended			36 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2007 HSBC Securities [Member]	Jun. 30, 2013 Available-for-sale Securities [Member]	Dec. 31, 2012 Available-for-sale Securities [Member]	Jun. 30, 2013 Trading Assets [Member]	Dec. 31, 2012 Trading Assets [Member]	Jun. 30, 2013 Financial Guarantee [Member] Collateralized Securities [Member]
Guarantor Obligations [Line Items]
Outstanding financial standby letters of credit	$ 5,100,000,000		$ 5,100,000,000		$ 5,600,000,000
Outstanding financial standby performance guarantees	3,100,000,000		3,100,000,000		2,900,000,000
Deferred fee on stand by letters of credit	45,000,000		45,000,000		46,000,000
Allowance for credit losses on unfunded standby letters of credit	17,000,000		17,000,000		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	13,300,000,000		13,300,000,000		15,100,000,000
Principal amount outstanding on loans from our legacy broker channel	8,500,000,000		8,500,000,000		9,600,000,000
Repurchase demands received from our legacy broker channel	44,000,000	151,000,000	120,000,000	233,000,000
Range of possible losses in excess of recorded repurchase liability, minimum											0
Range of possible losses in excess of recorded repurchase liability, maximum											130,000,000
Liquidity facilities	3,400,000,000		3,400,000,000		2,200,000,000
Securities available-for-sale							8,400,000,000	6,500,000,000
Fair value of collateral received									3,600,000,000	2,200,000,000
Separately reported available-for-sale pledged assets	9,200,000,000		9,200,000,000		5,700,000,000
Securities sold under agreements to repurchase	8,200,000,000		8,200,000,000		1,300,000,000
Whole loan securitization						$ 24,000,000,000