Related Party Transactions - Narrative (Details)		12 Months Ended
		Dec. 31, 2024 USD ($) borrowing	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Related Party Transaction [Line Items]
Long-term debt	[1]	$ 20,717,000,000	$ 18,661,000,000
Loans receivable from related parties	[1]	62,753,000,000	58,987,000,000
Notional value of derivative contracts		1,307,707,000,000	1,301,082,000,000
Preferred stock issued		265,000,000	265,000,000
Preferred stock outstanding		265,000,000	265,000,000
Return of capital to parent		0	0	$ 2,000,000,000
HSBC North America
Related Party Transaction [Line Items]
Return of capital to parent		100,000,000
HNAH
Related Party Transaction [Line Items]
Long-term debt		8,400,000,000	6,500,000,000
Maximum borrowing capacity		4,000,000,000.0
Amount outstanding under the loan agreement		0	0
Preferred stock issued		265,000,000	265,000,000
Preferred stock outstanding		265,000,000	265,000,000
HNAH | Loans And Lines Of Credit
Related Party Transaction [Line Items]
Loans receivable from related parties		3,000,000,000	1,300,000,000
HNAH | Loans And Lines Of Credit Maturing In The First Quarter Of 2025
Related Party Transaction [Line Items]
Loans receivable from related parties		1,400,000,000
HNAH | Loans And Lines Of Credit Maturing In The Second Quarter Of 2025
Related Party Transaction [Line Items]
Loans receivable from related parties		1,600,000,000
HMUS | Loans And Lines Of Credit
Related Party Transaction [Line Items]
Extended loans and lines of credit		14,300,000,000	13,300,000,000
Loans receivable from related parties		2,013,000,000	1,318,000,000
Other HSBC affiliates | Loans And Lines Of Credit
Related Party Transaction [Line Items]
Extended loans and lines of credit		3,500,000,000
Loans receivable from related parties		0	0
Other HSBC affiliates | Short Term Lending
Related Party Transaction [Line Items]
Loans receivable from related parties		436,000,000	0
Related Party
Related Party Transaction [Line Items]
Long-term debt		8,388,000,000	6,511,000,000
Loans receivable from related parties		5,449,000,000	2,618,000,000
Notional value of derivative contracts		735,500,000,000	719,600,000,000
Fair value of derivative assets and liabilities		126,000,000	$ 29,000,000
Fixed Rate Note Maturing June 2025 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		2,000,000,000.0
Fixed Rate Note Maturing September 2025 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		2,000,000,000.0
Fixed Rate Note Maturing December 2027 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		500,000,000
Fixed Rate Note Maturing December 2028 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		500,000,000
Fixed Rate Note Maturing June 2030 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		1,500,000,000
Fixed Rate Note Maturing September 2029 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		300,000,000
Fixed Rate Note Maturing November 2025 to November 2031 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		$ 1,600,000,000
Number of equal borrowings | borrowing		7

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2024 and 2023. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 27, "Variable Interest Entities," for additional information. At December 31,20242023(in millions)AssetsOther assets$11 $23 Total assets$11 $23 LiabilitiesInterest, taxes and other liabilities$4 $17 Total liabilities$4 $17