Carrying Value of Those Assets Measured at Fair Value on a Non-Recurring Basis (Detail) (Fair Value, Measurements, Nonrecurring, USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Loans Held-for-Sale
Assets measured at fair value on a non-recurring basis	$ 56	$ 212
Loans Held For Investment [Member]
Assets measured at fair value on a non-recurring basis	12	72
Other Real Estate Owned
Assets measured at fair value on a non-recurring basis	411	479
Affordable Housing
Assets measured at fair value on a non-recurring basis		324
Other Assets
Assets measured at fair value on a non-recurring basis	99	45
Fair Value, Inputs, Level 1 [Member] | Loans Held-for-Sale
Assets measured at fair value on a non-recurring basis	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
Fair Value, Inputs, Level 1 [Member] | Other Real Estate Owned
Assets measured at fair value on a non-recurring basis	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
Assets measured at fair value on a non-recurring basis	0	0
Fair Value, Inputs, Level 2 [Member] | Loans Held-for-Sale
Assets measured at fair value on a non-recurring basis	56	108
Fair Value, Inputs, Level 2 [Member] | Loans Held For Investment [Member]
Assets measured at fair value on a non-recurring basis	0	0
Fair Value, Inputs, Level 2 [Member] | Other Real Estate Owned
Assets measured at fair value on a non-recurring basis	299	372
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
Assets measured at fair value on a non-recurring basis	24	24
Fair Value, Inputs, Level 3 [Member] | Loans Held-for-Sale
Assets measured at fair value on a non-recurring basis	0	104
Fair Value, Inputs, Level 3 [Member] | Loans Held For Investment [Member]
Assets measured at fair value on a non-recurring basis	12	72
Fair Value, Inputs, Level 3 [Member] | Other Real Estate Owned
Assets measured at fair value on a non-recurring basis	112	107
Fair Value, Inputs, Level 3 [Member] | Affordable Housing
Assets measured at fair value on a non-recurring basis		324
Fair Value, Inputs, Level 3 [Member] | Other Assets
Assets measured at fair value on a non-recurring basis	75	21
Valuation Allowance | Loans Held-for-Sale
Valuation Allowance	0	0
Valuation Allowance | Loans Held For Investment [Member]
Valuation Allowance	(1)	(7)
Valuation Allowance | Other Real Estate Owned
Valuation Allowance	(136)	(127)
Valuation Allowance | Affordable Housing
Valuation Allowance		0
Valuation Allowance | Other Assets
Valuation Allowance	$ (48)	$ (20)