Related Party Transactions - Summary of Loans (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
HSBC Finance Corporation [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	$ 3,014	$ 3,014
HMUS [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	978	563
HSBC Bank Brasil [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	0	1,108
HSBC Mexico [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	725	75
Other Affiliates [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	98	61
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	$ 4,815	$ 4,821