Income Taxes - Net Deferred Tax Position (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Deferred tax assets:
Allowance for credit losses	$ 265		$ 250
Employee benefit accruals	130		142
Accrued expenses	143		111
Unused tax benefit carry-forwards	16		46
Bond premium amortization	284		226
Future federal tax benefit of state uncertain tax reserves	6		171
Interests in real estate mortgage investment conduits	453	[1]	309	[1]
Other	398		499
Total deferred tax assets	1,695		1,754
Valuation allowance	(11)	[2]	0	[2]
Total deferred tax assets less valuation allowance	1,684		1,754
Less deferred tax liabilities:
Fair value adjustments	71		22
Unrealized gains (losses) on investment securities	103		(8)
Mortgage servicing rights	62		96
Capitalized costs	42		34
Others	53		53
Total deferred tax liabilities	331		197
Net deferred tax asset	$ 1,353		$ 1,557

[1] Real estate mortgage investment conduits ("REMICs") are investment vehicles that hold commercial and residential mortgages in trust and issue securities representing an undivided interest in these mortgages. HSBC Bank USA holds portfolios of noneconomic residual interests in a number of REMICs. This item represents tax basis in such interests which has accumulated as a result of tax rules requiring the recognition of income related to such noneconomic residuals.

[2] The deferred tax valuation allowance is attributed to state temporary differences that, based on available evidence, it is more-likely-than-not that the deferred tax asset will not be realized. The valuation allowance was established as a result of New York State Tax Reform that was enacted on March 31, 2014.