Fair Value Fair Value (Schedule of Availability of Significant Unobservable Inputs by Balance Sheet Classification) (Details) (Fair Value, Inputs, Level 3 [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure	$ 6,820
Liabilities, Fair Value Disclosure	155
Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure	632
Liabilities, Fair Value Disclosure	135
Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure	6,188
Liabilities, Fair Value Disclosure	20
Collateralized Mortgage Backed Securities [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	912
Collateralized Mortgage Backed Securities [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	912
Asset-backed Securities, Student Loans [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	511
Asset-backed Securities, Student Loans [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	315
Asset-backed Securities, Student Loans [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	196
Asset-backed Securities, Credit Cards [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	119
Asset-backed Securities, Credit Cards [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	31
Asset-backed Securities, Credit Cards [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	88
Asset-backed Securities, Other [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	3,090
Asset-backed Securities, Other [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	104
Asset-backed Securities, Other [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	2,986
Non-US Debt Securities, Mortgage-Backed Securities [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	469
Non-US Debt Securities, Mortgage-Backed Securities [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0
Non-US Debt Securities, Mortgage-Backed Securities [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	469
Non-US Debt Securities, Asset-Backed Securities [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	1,035
Non-US Debt Securities, Asset-Backed Securities [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0
Non-US Debt Securities, Asset-Backed Securities [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	1,035
Non-US Debt Securities, Other [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	314
Non-US Debt Securities, Other [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	5
Non-US Debt Securities, Other [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	309
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	50
US States and Political Subdivisions Debt Securities [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	50
US States and Political Subdivisions Debt Securities [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0
Collateralized Mortgage Obligations [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	193
Collateralized Mortgage Obligations [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0
Collateralized Mortgage Obligations [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Available-for-sale Securities, Fair Value Disclosure	193
Other Debt Obligations [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Other Liabilities, Fair Value Disclosure	20
Other Debt Obligations [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Other Liabilities, Fair Value Disclosure	0
Other Debt Obligations [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Other Liabilities, Fair Value Disclosure	20
Derivative Financial Instruments, Liabilities [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	126
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	9
Derivative Financial Instruments, Liabilities [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	126
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	9
Derivative Financial Instruments, Assets [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	127
Derivative Financial Instruments, Assets [Member] | Significant Unobservable Inputs Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	127
Derivative Financial Instruments, Assets [Member] | Significant Unobservable Inputs Not Readily Available [Member]
Fair Value, Measurements, Availability of Significant Unobservable Inputs [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	$ 0