Related Party Transactions - Summary of Loans (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
HSBC Finance Corporation [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	$ 3,013	$ 3,014
HMUS [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	1,043	978
HSBC Mexico [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	729	725
Other Affiliates [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	322	98
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	$ 5,107	$ 4,815