Guarantee Arrangements and Pledged Assets and Collateral - Additional Information (Detail) (USD $)	12 Months Ended					36 Months Ended	3 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2007	Dec. 31, 2013		Mar. 31, 2014	Dec. 31, 2011
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 128,894,000,000		$ 191,349,000,000				$ 191,349,000,000
Collateral accepted under security repurchase agreements but not reported on the balance sheet that can be sold or repledged, fair value	6,765,000,000		4,187,000,000				4,187,000,000
Collateral accepted under security repurchase agreements that has been sold or repledged under repurchase agreements or to cover short sales	2,226,000,000		2,771,000,000				2,771,000,000
Net rental expense	147,000,000		149,000,000		147,000,000
Hsbc Securities [Member]
Guarantor Obligations [Line Items]
Whole loan securitization						24,000,000,000
Securities available-for-sale [Member]
Guarantor Obligations [Line Items]
Securities pledged as collateral that can be sold or repledged by the secured party, fair value	8,348,000,000		10,950,000,000				10,950,000,000
Trading Securities [Member]
Guarantor Obligations [Line Items]
Securities pledged as collateral that can be sold or repledged by the secured party, fair value	2,886,000,000		1,296,000,000				1,296,000,000
Financial standby letters of credit, net of participations [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	5,358,000,000	[1],[2]	5,237,000,000	[1],[2]			5,237,000,000	[1],[2]
Performance (non-financial) guarantees, net of participations [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	3,083,000,000	[1],[2]	3,172,000,000	[1],[2]			3,172,000,000	[1],[2]
Liquidity asset purchase agreements [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,685,000,000	[1]	2,560,000,000	[1]			2,560,000,000	[1]
Obligation to Repurchase Receivables Sold [Member]
Guarantor Obligations [Line Items]
Settlement of liability	31,000,000		141,000,000		152,000,000
Loss Contingency Accrual	27,000,000		99,000,000		219,000,000		99,000,000			237,000,000
Range of possible losses in excess of recorded repurchase liability, minimum	0
Range of possible losses in excess of recorded repurchase liability, maximum	25,000,000
Obligation to Repurchase Receivables Sold [Member] | Federal National Mortgage Association [Member]
Guarantor Obligations [Line Items]
Settlement of liability							83,000,000
Release of repurchase reserves							15,000,000
Obligation to Repurchase Receivables Sold [Member] | Federal Home Loan Mortgage Corporation [Member]
Guarantor Obligations [Line Items]
Settlement of liability									25,000,000
Release of repurchase reserves									34,000,000
Other liabilities [Member]
Guarantor Obligations [Line Items]
Allowance for credit losses on unfunded standby letters of credit	16,000,000		18,000,000				18,000,000
Other liabilities [Member] | Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Deferred fees on standby letters of credit	$ 50,000,000		$ 46,000,000				$ 46,000,000

[1] For standby letters of credit and liquidity asset purchase agreements, maximum loss represents losses to be recognized assuming the letter of credit and liquidity facilities have been fully drawn and the obligors have defaulted with zero recovery.

[2] Includes $937 million and $865 million issued for the benefit of HSBC affiliates at December 31, 2014 and 2013, respectively.