Related Party Transactions - Summary of Loans (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
HSBC Finance Corporation [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	$ 3,014	$ 3,014
HMUS [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	506	563
HSBC Bank Brasil [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	1,102	1,108
HSBC Mexico [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	725	75
Other Affiliates [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	100	61
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	$ 5,447	$ 4,821