Loans - Components of Loans (Details) - USD ($) $ in Millions	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 72,563		$ 73,875		$ 82,917
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	53,035		54,216
Commercial Loans [Member] | Real Estate, Including Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,533		10,890		10,000
Commercial Loans [Member] | Business and Corporate Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	12,504		14,080		14,365
Commercial Loans [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	20,088	[1],[2]	23,481	[1],[2]	29,905
Commercial Loans [Member] | Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	9,910	[1]	5,765	[1]	8,183
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	19,528		19,659
Consumer Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	17,273		17,181		17,758
Consumer Loans [Member] | Home Equity Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,191	[3]	1,408		1,600
Consumer Loans [Member] | Credit Cards [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	721	[4]	688		699
Consumer Loans [Member] | Other consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 343		$ 382		$ 407

[1] During 2017, in conjunction with the creation of the new Corporate Center segment as discussed further in Note 22, "Business Segments," we reclassified loans to HSBC affiliates from global banking to other commercial and revised prior periods to conform with the current year presentation. As a result, other commercial includes loans to HSBC affiliates which totaled $6,750 million and $3,274 million at December 31, 2017 and 2016, respectively. All tables below have been restated to reflect this reclassification, as applicable. See Note 21, "Related Party Transactions," for additional information regarding loans to HSBC affiliates.

[2] Represents large multinational firms including globally focused U.S. corporate and financial institutions, U.S. dollar lending to multinational banking clients managed by HSBC on a global basis and complex large business clients supported by Global Banking and Markets relationship managers.

[3] Home equity mortgage maturities reflect estimates based on historical payment patterns.

[4] As credit card receivables do not have stated maturities, the table reflects estimates based on historical payment patterns.