Loans - Status of Commercial Loan Portfolio (Detail) - USD ($) $ in Millions		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Accruing Loans Contractually Past Due 90 days or More		$ 18		$ 17
Total loans		73,875		82,917		$ 77,741
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		53,425		62,187
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest		790		265
Accruing Loans Contractually Past Due 90 days or More		1		1
Total loans		54,216		62,453
Commercial Loans [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		10,834		9,947
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest		56		53
Accruing Loans Contractually Past Due 90 days or More		0		0
Total loans		10,890		10,000		10,300
Commercial Loans [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		13,892		14,197
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest		187		167
Accruing Loans Contractually Past Due 90 days or More		1		1
Total loans	[1]	14,080		14,365		13,878
Commercial Loans [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		26,209		34,676
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest		546		44
Accruing Loans Contractually Past Due 90 days or More		0		0
Total loans	[1]	26,755	[2]	34,720	[2]	30,328
Commercial Loans [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		2,490		3,367
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest		1		1
Accruing Loans Contractually Past Due 90 days or More		0		0
Total loans		$ 2,491		$ 3,368		$ 3,581

[1] During the fourth quarter of 2016, we transferred certain customer relationships from CMB to GB&M as discussed further in Note 22, "Business Segments," in the accompanying consolidated financial statements. As a result, we reclassified $4.8 billion, $3.9 billion and $3.4 billion of loans and $27 million, $24 million and $7 million of allowance for credit losses from business and corporate banking to global banking at December 31, 2015, 2014 and 2013, respectively, to conform with the current year presentation.

[2] Represents large multinational firms including globally focused U.S. corporate and financial institutions, U.S. dollar lending to multinational banking customers managed by HSBC on a global basis and complex large business customers supported by GB&M relationship managers. Also includes loans to HSBC affiliates which totaled $3,274 million and $4,815 million at December 31, 2016 and 2015, respectively. See Note 21, "Related Party Transactions," for additional information regarding loans to HSBC affiliates.