Loans - Status of Commercial Loan Portfolio (Detail) - USD ($) $ in Millions	Jun. 30, 2016		Dec. 31, 2015		Jun. 30, 2015
Financing Receivable, Recorded Investment [Line Items]
Accruing Loans Contractually Past Due 90 days or More	$ 17		$ 17
Total loans	79,810		82,917		$ 83,617
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	58,613		62,187
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest	929		265
Accruing Loans Contractually Past Due 90 days or More	1		1
Total loans	59,543		62,453
Commercial Loans [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	10,926		9,947
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest	47		53
Accruing Loans Contractually Past Due 90 days or More	0		0
Total loans	10,973		10,000		11,520
Commercial Loans [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	18,836		18,948
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest	238		167
Accruing Loans Contractually Past Due 90 days or More	1		1
Total loans	19,075		19,116		19,712
Commercial Loans [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	25,714		29,925
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest	643		44
Accruing Loans Contractually Past Due 90 days or More	0		0
Total loans	26,357	[1]	29,969	[1]	28,942
Commercial Loans [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	3,137		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	$ 3,138		$ 3,368		$ 3,422

[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. Also includes loans to HSBC affiliates which totaled $5,072 million and $4,815 million at June 30, 2016 and December 31, 2015, respectively. See Note 14, "Related Party Transactions," for additional information regarding loans to HSBC affiliates.