Loans - Components of Loans (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 67,710		$ 63,258		$ 61,452
Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	48,509		44,150
Total loans	48,509		44,150
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	8,919		8,457
Total loans	8,919		8,457		7,920
Commercial Loan [Member] | Business and Corporate Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	13,668		12,608
Total loans	13,668		12,608		12,497
Commercial Loan [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	23,370	[1],[2]	20,009	[1],[2]
Total loans	23,370		20,009		19,011
Commercial Loan [Member] | Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	2,552		3,076
Total loans	2,552		3,076		3,140
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	19,201		19,108
Total loans	19,201		19,108
Consumer Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	15,720		15,371
Total loans	15,720		15,371		15,086
Consumer Loans [Member] | Home Equity Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,087		2,324		2,387
Consumer Loans [Member] | Credit Card Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	856		815
Total loans	856		815		796
Consumer Loans [Member] | Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	538		598
Total loans	538		598		615
Home Equity Mortgages [Member] | Home Equity Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer			2,324
Total loans	$ 2,087

[1] Represents large multinational firms including globally focused U.S. corporate and financial institutions and U.S. Dollar lending to multinational banking customers managed by HSBC on a global basis as well as loans to HSBC affiliates.

[2] Includes loans to HSBC affiliates of $5.9 billion and $4.5 billion at September 30, 2013 and December 31, 2012, respectively. See Note 14, "Related Party Transactions" for additional information regarding loans to HSBC affiliates.