Estimated Fair Value Of Financial Instruments (Narrative) (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets transferred from level 2 to level 3	$ 365,000,000	$ 131,000,000	$ 887,000,000	$ 631,000,000
Derivative assets transferred from level 3 to level 2	34,000,000		141,000,000	310,000,000
OREO [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Appraisal value to be reviewed	250,000		250,000
Appraisal value subject to technical review	1,000,000		1,000,000
Collateral-Dependent Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans updated for appraisal in excess	500,000		500,000
Appraisal value subject to technical review	1,000,000		1,000,000
Collateral-Dependent Impaired Loans [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Appraisal value to be reviewed	250,000		250,000
Collateral-Dependent Impaired Loans [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Appraisal value to be reviewed	$ 500,000		$ 500,000