Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Beginning balance		$ 484		$ 437		$ 278
Included in earnings		399		122		233
Purchases		(2)		(1)		(2)
Sale and exercise of warrant		(477)
Sales				(1)
Settlements		(111)		(102)		(106)
Transfers into Level 3		87	[1]	29	[2]	34	[3]
Ending balance		380		484		437
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held		83	[4]	10	[5]	185	[6]
Trading Securities
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Beginning balance				1		1
Sales				(1)
Ending balance						1
Residential Mortgage
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Beginning balance		108		92		76
Included in earnings				4		(1)
Settlements		(28)		(17)		(17)
Transfers into Level 3		87	[1]	29	[2]	34	[3]
Ending balance		167		108		92
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held				4	[5]	(1)	[6]
Interest Rate Contract
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Beginning balance		10	[7],[8]	8	[7],[9]	57	[9]
Included in earnings		111	[8]	125	[7]	59	[9]
Purchases		(2)	[8]	(1)	[7]	(2)	[9]
Settlements		(107)	[8]	(122)	[7]	(106)	[9]
Ending balance		12	[8]	10	[7],[8]	8	[7],[9]
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held		17	[4],[8]	13	[5],[7]	11	[6],[9]
Equity Contract
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Beginning balance		366	[7],[8]	336	[7],[9]	144	[9]
Included in earnings		288	[8]	(7)	[7]	175	[9]
Sale and exercise of warrant	[8]	(477)
Settlements		24	[8]	37	[7]	17	[9]
Ending balance		201	[8]	366	[7],[8]	336	[7],[9]
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held		$ 66	[4],[8]	$ (7)	[5],[7]	$ 175	[6],[9]

[1] Includes residential mortgage loans held for sale that were transferred to held for investment.

[2] Includes residential mortgage loans held for sale that were transferred to held for investment.

[3] Includes residential mortgage loans held for sale that were transferred to held for investment.

[4] Includes interest income and expense.

[5] Includes interest income and expense.

[6] Includes interest income and expense.

[7] Net interest rate derivatives include derivative assets and liabilities of $12 and $2, respectively as of December 31, 2014. Net equity derivatives include derivative assets and liabilities of $415 and $49, respectively, as of December 31, 2014.

[8] Net interest rate derivatives include derivative assets and liabilities of $15 and $3, respectively, as of December 31, 2015. Net equity derivatives include derivative assets and liabilities of $262 and $61, respectively, as of December 31, 2015.

[9] Net interest rate derivatives include derivative assets and liabilities of $12 and $4, respectively, as of December 31, 2013. Net equity derivatives include derivative assets and liabilities of $384 and $48, respectively, as of December 31, 2013.