Carrying Value of Those Assets Measured at Fair Value on a Non-Recurring Basis (Detail) (Fair Value, Measurements, Nonrecurring [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 65,000,000	$ 212,000,000
Loans Held For Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	308,000,000	72,000,000
Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	264,000,000	479,000,000
Affordable Housing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	82,000,000	324,000,000
Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	65,000,000	45,000,000
Fair Value, Inputs, Level 1 [Member] | Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Loans Held For Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Affordable Housing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	65,000,000	108,000,000
Fair Value, Inputs, Level 2 [Member] | Loans Held For Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	205,000,000	372,000,000
Fair Value, Inputs, Level 2 [Member] | Affordable Housing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	42,000,000	24,000,000
Fair Value, Inputs, Level 3 [Member] | Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	104,000,000
Fair Value, Inputs, Level 3 [Member] | Loans Held For Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	308,000,000	72,000,000
Fair Value, Inputs, Level 3 [Member] | Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	59,000,000	107,000,000
Fair Value, Inputs, Level 3 [Member] | Affordable Housing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	82,000,000	324,000,000
Fair Value, Inputs, Level 3 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	23,000,000	21,000,000
Valuation Allowance [Member] | Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges	0	0
Valuation Allowance [Member] | Loans Held For Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges	(79,000,000)	0
Valuation Allowance [Member] | Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges	(48,000,000)	(9,000,000)
Valuation Allowance [Member] | Affordable Housing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges	(96,000,000)	(10,000,000)
Valuation Allowance [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges	$ (13,000,000)	$ (17,000,000)