Fair Value Fair Value (Fair Value Inputs, Assets and Liabilities, Quantitative Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2012
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Assumptions, Expected Term	10 years 9 months 21 days
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	6,931
Liabilities, Fair Value Disclosure	166
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Student Loans [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	484
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Credit Cards [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	274
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Other [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	3,094
Fair Value, Inputs, Level 3 [Member] | Non-US Debt Securities, Other [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	1
Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	49
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	157
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	9
Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Asset-backed Securities, Student Loans [Member] | Weighted Average [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Credit Spread Risk	8.40%
Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Asset-backed Securities, Credit Cards [Member] | Weighted Average [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Credit Spread Risk	2.90%
Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Asset-backed Securities, Other [Member] | Weighted Average [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Credit Spread Risk	1.30%
Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Non-US Debt Securities, Other [Member] | Weighted Average [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	0.30%
Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | US States and Political Subdivisions Debt Securities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Credit Spread Risk	1.90%
Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Derivative Financial Instruments, Liabilities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Participant Redemptions	6.40%
Fair Value, Inputs, Level 3 [Member] | Option Model Approach Valuation Technique [Member] | Derivative Financial Instruments, Liabilities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Assumptions, Expected Volatility Rate	11.20%
Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	160
Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Option Model Approach Valuation Technique [Member] | Weighted Average [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Assumptions, Expected Volatility Rate	11.30%
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	463	[1]
Liabilities, Fair Value Disclosure	166	[1]
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Student Loans [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	11	[1]
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Credit Cards [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	138	[1]
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities, Other [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	104	[1]
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Non-US Debt Securities, Other [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	1	[1]
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	49	[1]
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	157	[1]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	9	[1]
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Asset-backed Securities, Student Loans [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	11
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Asset-backed Securities, Credit Cards [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	138
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Asset-backed Securities, Other [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	104
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Non-US Debt Securities, Other [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	1
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale Securities, Fair Value Disclosure	49
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	9
Significant Unobservable Inputs Readily Available [Member] | Fair Value, Inputs, Level 3 [Member] | Option Model Approach Valuation Technique [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	157
Significant Unobservable Inputs Readily Available [Member] | Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	160	[1]
Significant Unobservable Inputs Readily Available [Member] | Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Option Model Approach Valuation Technique [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	160

[1] Information with respect to these model-priced financial assets and liabilities is provided in the preceding table.