Related Party Transactions - Summary of Loans (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 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	764	563
HSBC Bank Brasil [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	1,110	1,108
Other Affiliates [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	128	136
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Loans and Leases Receivable, Related Parties	$ 5,016	$ 4,821