Related Party Transactions - Summary of Loans (Details) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Loans, net	[1]	$ 59,797	$ 58,987
HMUS and subsidiaries | Loans And Lines Of Credit
Related Party Transaction [Line Items]
Loans, net		2,140	1,318
HSBC North America | Loans And Lines Of Credit
Related Party Transaction [Line Items]
Loans, net		1,300	1,300
Other short-term affiliate lending | Loans And Lines Of Credit
Related Party Transaction [Line Items]
Loans, net		0	0
Other short-term affiliate lending | Short Term Lending
Related Party Transaction [Line Items]
Loans, net		2	0
Related Party
Related Party Transaction [Line Items]
Loans, net		$ 3,442	$ 2,618

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at March 31, 2024 and December 31, 2023. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 15, "Variable Interest Entities," for additional information. March 31, 2024December 31, 2023(in millions)AssetsOther assets$21 $23 Total assets$21 $23 LiabilitiesInterest, taxes and other liabilities$28 $17 Total liabilities$28 $17