Related Party Transactions - Additional Information (Details) - USD ($)		3 Months Ended	12 Months Ended
		Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Long-term debt	[1]	$ 17,236,000,000	$ 17,236,000,000	$ 19,979,000,000
Notional value of derivative contracts		1,395,345,000,000	1,395,345,000,000	2,021,133,000,000
Preferred stock issued		1,265,000,000	1,265,000,000	1,265,000,000
Preferred stock outstanding		1,265,000,000	1,265,000,000	1,265,000,000
Return of capital to parent			1,000,000,000	0	$ 2,400,000,000
HNAH
Related Party Transaction [Line Items]
Return of capital to parent		1,000,000,000
HNAH
Related Party Transaction [Line Items]
Long-term debt		5,500,000,000	5,500,000,000	2,900,000,000
Maximum borrowing capacity		4,000,000,000	4,000,000,000
Amount outstanding under the loan agreement		0	0	0
Loans receivable from related parties		1,000,000,000	1,000,000,000	0
Preferred stock issued		1,265,000,000	1,265,000,000	1,265,000,000
Preferred stock outstanding		1,265,000,000	1,265,000,000	1,265,000,000
HMUS
Related Party Transaction [Line Items]
Extended loans and lines of credit		11,900,000,000	11,900,000,000	12,000,000,000
Amount outstanding on line of credit		1,600,000,000	1,600,000,000	1,100,000,000
Loans receivable from related parties		1,576,000,000	1,576,000,000	1,088,000,000
Other HSBC affiliates
Related Party Transaction [Line Items]
Extended loans and lines of credit		4,000,000,000	4,000,000,000	4,700,000,000
Amount outstanding on line of credit		0	0	0
Loans receivable from related parties		217,000,000	217,000,000	12,000,000
Affiliated Entity
Related Party Transaction [Line Items]
Long-term debt		5,511,000,000	5,511,000,000	2,878,000,000
Loans receivable from related parties		2,793,000,000	2,793,000,000	1,100,000,000
Notional value of derivative contracts		753,200,000,000	753,200,000,000	923,600,000,000
Fair value of derivative assets and liabilities		127,000,000	127,000,000	$ 66,000,000
Fixed Rate Note Maturing September 2025 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		2,000,000,000	2,000,000,000
Fixed Rate Note Maturing June 2030 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		1,500,000,000	1,500,000,000
Fixed Rate Note Maturing June 2025 | HNAH | Senior debt:
Related Party Transaction [Line Items]
Long-term debt		$ 2,000,000,000	$ 2,000,000,000

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2021 and 2020. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 27, "Variable Interest Entities," for additional information. At December 31,20212020(in millions)AssetsLoans$46 $10 Other assets55 79 Total assets$101 $89 LiabilitiesInterest, taxes and other liabilities$9 $10 Total liabilities$9 $10