Fair Value Measurements (Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs) (Level 3) (Detail) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		$ 412		$ 633		$ 380		$ 484
Included in earnings		28		161		133		280
Purchases		(1)				(2)		(1)
Settlements		(42)		(35)		(120)		(88)
Transfers Into Level 3	[1]	3		2		9		86
Ending Balance		400		761		400		761
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	[2]	19		142		40		210
Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		154		178		167		108
Included in earnings		0		1		3		2
Purchases		0				0		0
Settlements		(8)		(8)		(30)		(23)
Transfers Into Level 3	[1]	3		2		9		86
Ending Balance		149		173		149		173
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	[2]	0		1		3		2
Interest Rate Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		30	[3]	10		12	[3]	10	[4]
Included in earnings		42	[3]	38	[4]	127	[3]	90	[4]
Purchases		(1)	[3]			(2)	[3]	(1)	[4]
Settlements		(42)	[3]	(32)	[4]	(108)	[3]	(83)	[4]
Transfers Into Level 3	[1]	0	[3]	0	[4]	0	[3]	0	[4]
Ending Balance		29	[3]	16	[4]	29	[3]	16	[4]
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	[2]	33	[3]	19	[4]	34	[3]	20	[4]
Equity Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		228	[3]	445		201	[3]	366	[4]
Included in earnings		(14)	[3]	122	[4]	3	[3]	188	[4]
Purchases		0	[3]			0	[3]	0	[4]
Settlements		8	[3]	5	[4]	18	[3]	18	[4]
Transfers Into Level 3	[1]	0	[3]	0	[4]	0	[3]	0	[4]
Ending Balance		222	[3]	572	[4]	222	[3]	572	[4]
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	[2]	$ (14)	[3]	$ 122	[4]	$ 3	[3]	$ 188	[4]

[1] Includes certain residential mortgage loans originated as held for sale that were transferred to held for invest ment.

[2] Includes interest income and expense.

[3] Net interest rate derivatives include derivative assets and liabilities of $ 33 and $ 4 , respectively , as of September 30, 2016 . Net equity derivatives include derivative assets and liabilities of $ 325 and $ 103 , respectively, as of September 30, 2016 .

[4] Net interest rate derivatives include derivative assets and liabilities of $19 and $3 , respectively, as of September 30, 2015 . Net equity derivatives include derivativ e assets and liabilities of $630 and $5 8 , respectively, as of September 30, 2015 .