Loans - Components of Loans (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 62,932		$ 63,258		$ 53,869
Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	43,639		44,150
Total loans	43,639		44,150
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	8,319		8,457
Total loans	8,319		8,457		7,777
Commercial Loan [Member] | Business Banking and Middle Markets Enterprises [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	12,725		12,608
Total loans	12,725		12,608		10,889
Commercial Loan [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	19,718	[1]	20,009	[1]
Total loans	19,718		20,009		13,852
Commercial Loan [Member] | Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial	2,877		3,076
Total loans	2,877		3,076		3,051
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	19,293		19,108
Total loans	19,293		19,108
Consumer Loans [Member] | Home Equity Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	2,236		2,324
Total loans	2,236		2,324		2,491
Consumer Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	15,730		15,371
Total loans	15,730		15,371		14,344
Consumer Loans [Member] | Credit Card Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	749		815
Total loans	749		815		786
Consumer Loans [Member] | Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total consumer	578		598
Total loans	$ 578		$ 598		$ 679

[1] Represents large multinational firms including globally focused U.S. corporate and financial institutions and USD lending to select high quality Latin American and other multinational customers managed by HSBC on a global basis.