Loans - Credit Risk Profile of Commercial Loans (Detail) - USD ($) $ in Millions		Jun. 30, 2016		Dec. 31, 2015		Jun. 30, 2015
Financing Receivable, Recorded Investment [Line Items]
Total loans		$ 79,810		$ 82,917		$ 83,617
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		59,543		62,453
Commercial Loans [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		10,973		10,000		11,520
Commercial Loans [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		19,075		19,116		19,712
Commercial Loans [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		26,357	[1]	29,969	[1]	28,942
Commercial Loans [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		3,138		3,368		$ 3,422
Internal Investment Grade [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	38,355		43,854
Internal Investment Grade [Member] | Commercial Loans [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	8,564		8,487
Internal Investment Grade [Member] | Commercial Loans [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	9,801		10,373
Internal Investment Grade [Member] | Commercial Loans [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	18,209		23,111
Internal Investment Grade [Member] | Commercial Loans [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	1,781		1,883
Internal Noninvestment Grade [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		21,188		18,599
Internal Noninvestment Grade [Member] | Commercial Loans [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		2,409		1,513
Internal Noninvestment Grade [Member] | Commercial Loans [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		9,274		8,743
Internal Noninvestment Grade [Member] | Commercial Loans [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		8,148		6,858
Internal Noninvestment Grade [Member] | Commercial Loans [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		$ 1,357		$ 1,485

[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.

[2] Investment grade includes commercial loans with credit ratings of at least BBB- or above or the equivalent based on our internal credit rating system.