Loans - Contractual Maturities (Details) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021		$ 24,160
2022		11,493
2023		5,571
2024		2,884
2025		1,202
Thereafter		16,778
Total loans		62,088		$ 68,553
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		41,599		48,211
Commercial Loans [Member] | Real Estate, Including Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021		5,791
2022		2,452
2023		1,256
2024		584
2025		167
Thereafter		214
Total loans		10,464		11,501
Commercial Loans [Member] | Business and Corporate Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021		7,460
2022		3,158
2023		1,617
2024		753
2025		215
Thereafter		276
Total loans	[1]	13,479		13,479
Commercial Loans [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021		7,482
2022		3,167
2023		1,622
2024		755
2025		215
Thereafter		278
Total loans	[2]	13,519		17,915
Commercial Loans [Member] | Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021		2,290
2022		969
2023		496
2024		231
2025		66
Thereafter		85
Total loans		4,137		5,316
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		20,489		20,342
Consumer Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021		563
2022		468
2023		486
2024		501
2025		500
Thereafter		15,859
Total loans		18,377		17,801
Consumer Loans [Member] | Home Equity Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021	[3]	322
2022	[3]	154
2023	[3]	93
2024	[3]	57
2025	[3]	37
Thereafter	[3]	64
Total loans		727	[3]	853
Consumer Loans [Member] | Credit Cards [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021	[4]	0
2022	[4]	1,066
2023	[4]	0
2024	[4]	0
2025	[4]	0
Thereafter	[4]	0
Total loans		1,066	[4]	1,405
Consumer Loans [Member] | Other consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2021		252
2022		59
2023		1
2024		3
2025		2
Thereafter		2
Total loans	[5]	$ 319		$ 283

[1] Includes loans funded under the PPP which totaled $1,043 million at December 31, 2020. PPP loans are fully guaranteed by the Small Business Administration, if certain conditions are met.

[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 an average estimate based on historical payment patterns

[5] Includes certain student loans that we have elected to designate under the fair value option and are therefore carried at fair value, which totaled $32 million at December 31, 2020. See Note 16, "Fair Value Option," for further details.