Related Party Transactions - Summary of Loans (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Related Party Transaction [Line Items]
Loans, net	$ 61,586	$ 59,894
HMUS and subsidiaries | Loans And Lines Of Credit
Related Party Transaction [Line Items]
Loans, net	3,100	1,800
HSBC North America | Loans And Lines Of Credit
Related Party Transaction [Line Items]
Loans, net	2,800	4,200
Related Party
Related Party Transaction [Line Items]
Loans, net	$ 5,900	$ 6,000