Fair Value Measurements - Fair Value Hierarchy Level within which Fair Value of Financial and Non-Financial Assets has Been Recorded (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	$ 0	[1]			$ 0	[1]
Fair Value, Measurements, Nonrecurring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	647				647				974
Total Gains (Losses)	(12)		(51)		(28)		(87)
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	22				22				24
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	383				383				610
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	242				242				340
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	202	[2]			202	[2]			77	[2]
Total Gains (Losses)	0	[2]	(4)	[2]	3	[2]	(6)	[2]
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage [Member] | Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	0	[2]			0	[2]			0	[2]
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	134	[2]			134	[2]			10	[2]
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	68	[2]			68	[2]			67	[2]
Fair Value, Measurements, Nonrecurring [Member] | Impaired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	129	[3]			129	[3]			155	[3]
Total Gains (Losses)	(1)	[3]	(12)	[3]	(2)	[3]	(23)	[3]
Fair Value, Measurements, Nonrecurring [Member] | Impaired loans [Member] | Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	0	[3]			0	[3]			0	[3]
Fair Value, Measurements, Nonrecurring [Member] | Impaired loans [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	0	[3]			0	[3]			0	[3]
Fair Value, Measurements, Nonrecurring [Member] | Impaired loans [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	129	[3]			129	[3]			155	[3]
Fair Value, Measurements, Nonrecurring [Member] | Impaired Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	294	[3]			294	[3]			718	[3]
Total Gains (Losses)	(11)	[3]	(35)	[3]	(31)	[3]	(60)	[3]
Fair Value, Measurements, Nonrecurring [Member] | Impaired Consumer Loans [Member] | Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	0	[3]			0	[3]			0	[3]
Fair Value, Measurements, Nonrecurring [Member] | Impaired Consumer Loans [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	249	[3]			249	[3]			600	[3]
Fair Value, Measurements, Nonrecurring [Member] | Impaired Consumer Loans [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	45	[3]			45	[3]			118	[3]
Fair Value, Measurements, Nonrecurring [Member] | Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	22	[1]			22	[1]			24	[1]
Total Gains (Losses)	0	[1]	0	[1]	2	[1]	2	[1]
Fair Value, Measurements, Nonrecurring [Member] | Commercial real estate [Member] | Level 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	22	[1]			22	[1]			24	[1]
Fair Value, Measurements, Nonrecurring [Member] | Commercial real estate [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements	0	[1]			0	[1]			0	[1]
Fair Value, Measurements, Nonrecurring [Member] | Commercial real estate [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Recurring Fair Volume Measurements									$ 0	[1]

[1] Real estate owned are required to be reported on the balance sheet net of transactions costs. The real estate owned amounts in the table above reflect the fair value unadjusted for transaction costs

[2] As of June 30, 2013 and December 31, 2012, the fair value of the loans held for sale was below cost. Certain residential mortgage loans held for sale have been classified as a Level 3 fair value measurement within the fair value hierarchy as the underlying real estate properties which determine fair value are illiquid assets as a result of market conditions and significant inputs in estimating fair value were unobservable. Additionally, the fair value of these properties is affected by, among other things, the location, the payment history and the completeness of the loan documentation.

[3] Certain commercial and consumer loans have undergone troubled debt restructurings and are considered impaired. As a matter of practical expedient, we measure the credit impairment of a collateral-dependent loan based on the fair value of the collateral asset. The collateral often involves real estate properties that are illiquid due to market conditions. As a result, these loans are classified as a Level 3 fair value measurement within the fair value hierarchy.