Related Party Transactions - Additional Information (Details) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Derivative, notional amount		$ 4,210,729,000,000		$ 4,210,729,000,000		$ 4,212,040,000,000
HSBC North America Inc. HNAI [Member]
Related Party Transaction [Line Items]
Maximum borrowing capacity		150,000,000		150,000,000		150,000,000
Amount outstanding under the loan agreement		0		0		0
HSBC Finance Corporation [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		3,013,000,000		3,013,000,000		3,014,000,000
HSBC Finance Corporation [Member] | Extended Uncommitted Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Extended loans and lines of credit		5,000,000,000.0		$ 5,000,000,000.0		5,000,000,000.0
Debt term				364 days
Maximum maturity for borrowings under uncommitted revolving credit agreement				5 years
Amount outstanding on line of credit		3,000,000,000		$ 3,000,000,000		3,000,000,000
Credit agreement, amount maturing September 2017		500,000,000		500,000,000
Credit agreement amount maturing January 2018		1,500,000,000		1,500,000,000
Credit agreement amount maturing September 2018		1,000,000,000		1,000,000,000
HSBC Finance Corporation [Member] | Extended committed revolving credit facility [Member]
Related Party Transaction [Line Items]
Extended loans and lines of credit		1,000,000,000		1,000,000,000		1,000,000,000
Amount outstanding on line of credit		0		0		0
HMUS [Member]
Related Party Transaction [Line Items]
Extended loans and lines of credit		10,700,000,000		10,700,000,000		10,700,000,000
Loans and leases receivable from related parties		588,000,000		588,000,000		978,000,000
Amount outstanding on line of credit		588,000,000		588,000,000		978,000,000
HSBC Mexico [Member]
Related Party Transaction [Line Items]
Extended loans and lines of credit		1,200,000,000		1,200,000,000		1,200,000,000
Loans and leases receivable from related parties		725,000,000		725,000,000		725,000,000
Other Affiliates [Member]
Related Party Transaction [Line Items]
Extended loans and lines of credit		3,100,000,000		3,100,000,000
Loans and leases receivable from related parties		17,000,000		17,000,000		40,000,000
Regency [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	[1]	729,000,000		729,000,000		58,000,000
Notional amount of liquidity facilities		3,800,000,000		3,800,000,000		3,400,000,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		5,072,000,000		5,072,000,000		4,815,000,000
Derivative, notional amount		978,100,000,000		978,100,000,000		1,004,100,000,000
Fair value of derivative assets and liabilities		13,000,000		13,000,000		216,000,000
Floating Rate Notes [Member] | Hnah [Member] | Senior debt [Member]
Related Party Transaction [Line Items]
Debt issued		1,000,000,000		1,000,000,000		1,000,000,000.0
Floating Rate Notes [Member] | Hnah [Member] | Subordinated Debt [Member]
Related Party Transaction [Line Items]
Debt issued		900,000,000		900,000,000		900,000,000.0
Residential Mortgage [Member] | HSBC Finance Corporation [Member]
Related Party Transaction [Line Items]
Carrying amount of residential mortgage loans		636,000,000		636,000,000		$ 696,000,000
Support Services From Affiliates [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Rent from related party		15,000,000	$ 14,000,000	$ 31,000,000	$ 29,000,000
6.0 %, Non-Cumulative Series I Preferred Stock [Member] | Hnah [Member]
Related Party Transaction [Line Items]
HSBC USA preferred stock issued		$ 1,265,000,000
HSBC USA preferred stock dividend rate (percent)		6.00%

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