Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional values of derivative contracts	$ 2,193	$ 2,193	$ 8,933
Fair value of collateral agreements with affiliate counterparties	115	115	491
Decrease in debt carrying value due to fair value hedge	15	15	15
Losses on current derivative instruments designated as cash flow hedges are reported in OCI net of tax (less than $1 million at June 30, 2016)	1	1	15
Unrealized net losses on cash flow hedges (less than $1 million)		1
HSBC Bank USA [Member]
Derivative [Line Items]
Notional values of derivative contracts	2,200	2,200	8,900
Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Notional values of derivative contracts	0	0	2,624
Interest rate swaps [Member]
Derivative [Line Items]
Notional values of derivative contracts	0	0	1,859
Interest rate swaps [Member] | Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Notional values of derivative contracts	0	$ 0	$ 2,624
Notional value of terminated derivative contracts	$ 2,600