Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional values of derivative contracts	$ 7,074	$ 8,933
Fair value of collateral agreements with affiliate counterparties	537	491
Decrease in debt carrying value due to fair value hedge	15	15
Losses on current derivative instruments designated as cash flow hedges are reported in OCI net of tax and totaled a loss	7	15
Unrealized net losses on cash flow hedges	6
Unrealized net losses on cash flow hedges after tax	4
HSBC Bank USA [Member]
Derivative [Line Items]
Notional values of derivative contracts	7,100	8,900
Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Notional values of derivative contracts	2,624	$ 2,624
Terminated notional amount	$ 720