Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended										3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013 Trading Securities	Mar. 31, 2013 Trading Securities	Dec. 31, 2012 Trading Securities	Jun. 30, 2012 Trading Securities	Mar. 31, 2012 Trading Securities	Dec. 31, 2011 Trading Securities	Jun. 30, 2013 Residential Mortgage		Jun. 30, 2012 Residential Mortgage		Jun. 30, 2013 Residential Mortgage		Jun. 30, 2012 Residential Mortgage		Jun. 30, 2013 Interest Rate Contract		Jun. 30, 2012 Interest Rate Contract		Jun. 30, 2013 Interest Rate Contract		Jun. 30, 2012 Interest Rate Contract		Jun. 30, 2013 Equity Contract		Jun. 30, 2012 Equity Contract		Jun. 30, 2013 Equity Contract		Jun. 30, 2012 Equity Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	$ 304		$ 220		$ 278		$ 130		$ 1	$ 1	$ 1	$ 1	$ 1	$ 1	$ 81		$ 67		$ 76		$ 65		$ 48	[1]	$ 17	[1]	$ 57	[1]	$ 32	[1]	$ 174	[1]	$ 135	[1]	$ 144	[1]	$ 32	[1]
Total gains or losses (realized/unrealized):
Included in earnings	12		170		96		249								(2)				(1)				(57)	[1]	125	[1]	(1)	[1]	175	[1]	71	[1]	45	[1]	98	[1]	74	[1]
Settlements	20		87		85		81								4		3		7		6		21	[1]	88	[1]	86	[1]	153	[1]	(5)	[1]	(4)	[1]	(8)	[1]	78	[1]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Level 3 Transfers Net	8	[2]	12	[2]	15	[2]	17	[2]							8	[2]	12	[2]	15	[2]	17	[2]
Ending balance	304		315		304		315		1	1	1	1	1	1	83		76		83		76		(30)	[1]	54	[1]	(30)	[1]	54	[1]	250	[1]	184	[1]	250	[1]	184	[1]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Relating To Assets	$ 42	[3]	$ 99	[3]	$ 120	[3]	$ 145	[3]							$ (2)	[3]			$ (1)	[3]			$ (27)	[3]	$ 54	[3]	$ 23	[1],[3]	$ 71	[1]	$ 71	[3]	$ 45	[3]	$ 98	[1],[3]	$ 74	[3]

[1] Net interest rate derivatives include derivative assets and liabilities of $7 and $37, respectively, as of June 30, 2013 and $55 and $1, respectively, as of June 30, 2012. Net equity derivatives include derivative assets and liabilities of $287 and $37, respectively, as of June 30, 2013, and $214 and $30, respectively, as of June 30, 2012.

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

[3] Includes interest income and expense.