Carrying Value of Those Assets Measured at Fair Value on a Non-Recurring Basis (Detail) (Fair Value, Measurements, Nonrecurring, USD $)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Loans Held-for-Sale
Assets measured at fair value on a non-recurring basis	$ 17,000,000	$ 17,000,000	$ 212,000,000
Loans Held For Investment [Member]
Assets measured at fair value on a non-recurring basis	49,000,000	49,000,000	72,000,000
Other Real Estate Owned
Assets measured at fair value on a non-recurring basis	331,000,000	331,000,000	479,000,000
Affordable Housing
Assets measured at fair value on a non-recurring basis			324,000,000
Other Assets [Member]
Assets measured at fair value on a non-recurring basis	92,000,000	92,000,000	45,000,000
Fair Value, Inputs, Level 1 [Member] | Loans Held-for-Sale
Assets measured at fair value on a non-recurring basis	0	0	0
Fair Value, Inputs, Level 1 [Member] | Loans Held For Investment [Member]
Assets measured at fair value on a non-recurring basis	0	0	0
Fair Value, Inputs, Level 1 [Member] | Other Real Estate Owned
Assets measured at fair value on a non-recurring basis	0	0	0
Fair Value, Inputs, Level 1 [Member] | Affordable Housing
Assets measured at fair value on a non-recurring basis			0
Fair Value, Inputs, Level 1 [Member] | Other Assets [Member]
Assets measured at fair value on a non-recurring basis	0	0	0
Fair Value, Inputs, Level 2 [Member] | Loans Held-for-Sale
Assets measured at fair value on a non-recurring basis	17,000,000	17,000,000	108,000,000
Fair Value, Inputs, Level 2 [Member] | Loans Held For Investment [Member]
Assets measured at fair value on a non-recurring basis	0	0	0
Fair Value, Inputs, Level 2 [Member] | Other Real Estate Owned
Assets measured at fair value on a non-recurring basis	260,000,000	260,000,000	372,000,000
Fair Value, Inputs, Level 2 [Member] | Affordable Housing
Assets measured at fair value on a non-recurring basis			0
Fair Value, Inputs, Level 2 [Member] | Other Assets [Member]
Assets measured at fair value on a non-recurring basis	21,000,000	21,000,000	24,000,000
Fair Value, Inputs, Level 3 [Member] | Loans Held-for-Sale
Assets measured at fair value on a non-recurring basis	0	0	104,000,000
Fair Value, Inputs, Level 3 [Member] | Loans Held For Investment [Member]
Assets measured at fair value on a non-recurring basis	49,000,000	49,000,000	72,000,000
Fair Value, Inputs, Level 3 [Member] | Other Real Estate Owned
Assets measured at fair value on a non-recurring basis	71,000,000	71,000,000	107,000,000
Fair Value, Inputs, Level 3 [Member] | Affordable Housing
Assets measured at fair value on a non-recurring basis			324,000,000
Fair Value, Inputs, Level 3 [Member] | Other Assets [Member]
Assets measured at fair value on a non-recurring basis	71,000,000	71,000,000	21,000,000
Valuation Allowance | Loans Held-for-Sale
Valuation Allowance	0	0	0
Asset Impairment Charges	0	0	0
Valuation Allowance | Loans Held For Investment [Member]
Valuation Allowance	3,000,000	3,000,000	(7,000,000)
Asset Impairment Charges	0	0	0
Valuation Allowance | Other Real Estate Owned
Valuation Allowance	(136,000,000)	(136,000,000)	(127,000,000)
Asset Impairment Charges	0	3,000,000	(9,000,000)
Valuation Allowance | Affordable Housing
Valuation Allowance			0
Asset Impairment Charges			(10,000,000)
Valuation Allowance | Other Assets [Member]
Valuation Allowance	(60,000,000)	(60,000,000)	(20,000,000)
Asset Impairment Charges	$ (6,000,000)	$ (12,000,000)	$ (17,000,000)