Loans - Contractual Maturities (Details) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019		$ 20,246
2020		9,432
2021		7,046
2022		5,897
2023		8,369
Thereafter		17,988
Total loans		68,978		$ 72,563		$ 73,875
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		49,342		53,035
Commercial Loans [Member] | Real Estate, Including Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019		4,380
2020		1,750
2021		1,482
2022		1,231
2023		1,801
Thereafter		700
Total loans		11,344		10,533		10,890
Commercial Loans [Member] | Business and Corporate Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019		5,045
2020		2,016
2021		1,707
2022		1,418
2023		2,075
Thereafter		805
Total loans		13,066		12,504		14,080
Commercial Loans [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019		7,787
2020		3,111
2021		2,634
2022		2,189
2023		3,202
Thereafter		1,244
Total loans		20,167	[1]	20,088	[1]	23,481
Commercial Loans [Member] | Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019		1,840
2020		735
2021		622
2022		517
2023		757
Thereafter		294
Total loans		4,765	[2]	9,910	[2]	5,765
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		19,636		19,528
Consumer Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019		688
2020		453
2021		459
2022		456
2023		479
Thereafter		14,848
Total loans		17,383		17,273		17,181
Consumer Loans [Member] | Home Equity Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019	[3]	413
2020	[3]	216
2021	[3]	131
2022	[3]	80
2023	[3]	52
Thereafter	[3]	90
Total loans		982	[3]	1,191		1,408
Consumer Loans [Member] | Credit Cards [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019	[4]	0
2020	[4]	1,019
2021	[4]	0
2022	[4]	0
2023	[4]	0
Thereafter	[4]	0
Total loans		1,019	[4]	721		688
Consumer Loans [Member] | Other consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2019		93
2020		132
2021		11
2022		6
2023		3
Thereafter		7
Total loans		$ 252		$ 343		$ 382

[1] 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.

[2] Includes loans to HSBC affiliates which totaled $2,274 million and $6,750 million at December 31, 2018 and 2017, respectively. See Note 22, "Related Party Transactions," for additional information regarding loans to HSBC affiliates.

[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.