Additional Information about Derivative Assets and Liabilities Subject to Enforceable Master Netting Arrangement (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Derivative [Line Items]
Gross amounts recognized, derivatives assets	$ 672		$ 470
Gross amounts recognized, derivatives liabilities	718		942
Subject to enforceable master netting arrangement
Derivative [Line Items]
Gross amounts recognized, net derivatives	471		(166)
Gross amounts offset in the balance sheet, net derivatives	0		0
Net amounts presented in the balance sheet	471		(166)
Gross amounts not offset in the balance sheet, financial instruments, net derivatives	0	[1]	0	[1]
Gross amounts not offset in the balance sheet, collateral pledged/received	(444)		195
Over collateralization	(4)		(7)
Net amount	23		22
Derivative assets | Subject to enforceable master netting arrangement
Derivative [Line Items]
Gross amounts recognized, derivatives assets	707	[2]	496	[3]
Gross amounts offset in the balance sheet, derivatives assets	0	[2]	0	[3]
Net amounts presented in the balance sheet, derivatives assets	707	[2]	496	[3]
Gross amounts not offset in the balance sheet, financial instruments, derivative assets	(166)	[1],[2]	(286)	[1],[3]
Gross amounts not offset in the balance sheet, collateral pledged/received	(521)	[2]	(199)	[3]
Over collateralization	5	[2]	16	[3]
Net amount, derivatives assets	25	[2]	27	[3]
Derivative liabilities | Subject to enforceable master netting arrangement
Derivative [Line Items]
Gross amounts recognized, derivatives liabilities	236	[4]	662	[5]
Gross amounts offset in the balance sheet, derivatives liabilities	0	[4]	0	[5]
Net amounts presented in the balance sheet, derivatives liabilities	236	[4]	662	[5]
Gross amounts not offset in the balance sheet, financial instruments, derivative liabilities	(166)	[1],[4]	(286)	[1],[5]
Gross amounts not offset in the balance sheet, collateral pledged/received	(77)	[4]	(394)	[5]
Over collateralization	9	[4]	23	[5]
Net amount, derivatives liabilities	$ 2	[4]	$ 5	[5]

[1] Amounts represent derivative assets and/or liabilities that are presented gross within the balance sheet but are held with the same counterparty where we have a master netting arrangement. This adjustment results in presenting the net asset and net liability position for each counterparty.

[2] Included $43 million of accruals on derivatives classified as other assets and does not include amounts related to embedded derivatives.

[3] Included $25 million of accruals on derivatives classified as other assets and does not include amounts related to embedded derivatives.

[4] Included $26 million of accruals on derivatives classified as other liabilities and does not include amounts related to embedded derivatives and derivatives related to securitization entities.

[5] Included $7 million of accruals on derivatives classified as other liabilities and does not include amounts related to embedded derivatives and derivatives related to securitization entities.