Loans - Contractual Maturities (Details) - USD ($) $ in Millions		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020		$ 19,914
2021		9,256
2022		7,807
2023		7,332
2024		6,797
Thereafter		17,447
Total loans		68,553		$ 68,978		$ 72,563
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		48,211		49,342
Commercial Loans [Member] | Real Estate, Including Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020		4,517
2021		1,676
2022		1,712
2023		1,609
2024		1,515
Thereafter		472
Total loans		11,501		11,344		10,533
Commercial Loans [Member] | Business and Corporate Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020		5,293
2021		1,964
2022		2,006
2023		1,885
2024		1,775
Thereafter		556
Total loans		13,479		13,066		12,504
Commercial Loans [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020		7,157
2021		2,610
2022		2,667
2023		2,506
2024		2,238
Thereafter		737
Total loans		17,915	[1]	20,167	[1]	20,088
Commercial Loans [Member] | Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020		2,088
2021		775
2022		791
2023		744
2024		700
Thereafter		218
Total loans		5,316	[2]	4,765	[2]	9,910
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		20,342		19,636
Consumer Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020		393
2021		504
2022		501
2023		509
2024		518
Thereafter		15,376
Total loans		17,801		17,383		17,273
Consumer Loans [Member] | Home Equity Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	[3]	356
2021	[3]	189
2022	[3]	114
2023	[3]	70
2024	[3]	45
Thereafter	[3]	79
Total loans		853	[3]	982		1,191
Consumer Loans [Member] | Credit Cards [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	[4]	0
2021	[4]	1,405
2022	[4]	0
2023	[4]	0
2024	[4]	0
Thereafter	[4]	0
Total loans		1,405	[4]	1,019		721
Consumer Loans [Member] | Other consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020		110
2021		133
2022		16
2023		9
2024		6
Thereafter		9
Total loans		$ 283		$ 252		$ 343

[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] See Note 23, "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 an average estimate based on historical payment patterns.