Related Party Transactions - Summary of Loans (Details) - USD ($) $ in Millions		Sep. 30, 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		473	978
HSBC Mexico [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		975	725
Regency [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	[1]	0	58
Other Affiliates [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		2	40
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		$ 4,463	$ 4,815

[1] An asset-backed commercial paper conduit consolidated by an HSBC affiliate.