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		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	$ 519	$ 779	$ 519	$ 779
Fair Value Assets, Measured on Non-Recurring Basis, Gain Loss Included in Revenue		(19)	(28)	(75)
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	108	233	108	233
Fair Value Assets, Measured on Non-Recurring Basis, Gain Loss Included in Revenue	3	(10)	(4)	(16)
Residential Mortgage [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	108		108
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	65	71	65	71
Impaired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	309	415	309	415
Fair Value Assets, Measured on Non-Recurring Basis, Gain Loss Included in Revenue	(4)	(8)	(27)	44
Impaired loans [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	309		309
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	18	28	18	28
Fair Value Assets, Measured on Non-Recurring Basis, Gain Loss Included in Revenue	1	(1)	3	(4)
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	19	32	19	32
Capitalized Software Development Costs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value Assets, Measured on Non-Recurring Basis, Gain Loss Included in Revenue				(94)
Building Held For Sale [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value Assets, Measured on Non-Recurring Basis, Gain Loss Included in Revenue				(5)
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	37	65	37	65
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	482	714	482	714
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		5		5
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	108	228	108	228
Fair Value, Measurements, Nonrecurring [Member] | Consumer Loans [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	65	71	65	71
Fair Value, Measurements, Nonrecurring [Member] | Impaired loans [Member] | Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	309	415	309	415
Fair Value, Measurements, Nonrecurring [Member] | Commercial real estate [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	18	28	18	28
Fair Value, Measurements, Nonrecurring [Member] | Commercial Loans [Member] | Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	$ 19	$ 32	$ 19	$ 32