Fair Value (Fair Value Inputs, Assets and Liabilities, Quantitative Information) (Details) (Pricing Methods with Significant Unobservable Market Inputs (Level 3), USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013		Dec. 31, 2012
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets, fair value disclosure	6,568		6,980
Liabilities, fair value disclosure	162		115
Derivative instruments, liabilities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative instruments, foreign exchange contracts, liabilities	153		106
Derivative instruments, other, liabilities	9		9
Derivative instruments, assets
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative instruments, foreign exchange contracts, assets	172		113
Asset-backed securities, student loans
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	461		588
Asset-backed securities, credit cards
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	24		67
Asset-backed securities, other
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	3,872		3,994
State and political subdivisions
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	47		48
Discounted cash flows | Derivative instruments, liabilities | Weighted average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Participant redemptions	8.20%		6.70%
Discounted cash flows | Asset-backed securities, student loans | Weighted average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Credit spread	4.00%		6.70%
Discounted cash flows | Asset-backed securities, credit cards | Weighted average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Credit spread	2.10%		7.10%
Discounted cash flows | Asset-backed securities, other | Weighted average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Credit spread	2.00%		1.50%
Discounted cash flows | State and political subdivisions | Weighted average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Credit spread	1.70%		1.90%
Option model | Derivative instruments, liabilities | Weighted average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	12.40%		9.80%
Option model | Derivative instruments, assets | Weighted average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	12.00%		9.80%
Significant Unobservable Inputs Readily Available [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets, fair value disclosure	359	[1]	343	[1]
Liabilities, fair value disclosure	162	[1]	115	[1]
Significant Unobservable Inputs Readily Available [Member] | Derivative instruments, liabilities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative instruments, foreign exchange contracts, liabilities	153	[1]	106	[1]
Derivative instruments, other, liabilities	9	[1]	9	[1]
Significant Unobservable Inputs Readily Available [Member] | Derivative instruments, assets
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative instruments, foreign exchange contracts, assets	172	[1]	113	[1]
Significant Unobservable Inputs Readily Available [Member] | Asset-backed securities, student loans
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	14	[1]	12	[1]
Significant Unobservable Inputs Readily Available [Member] | Asset-backed securities, credit cards
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	24	[1]	67	[1]
Significant Unobservable Inputs Readily Available [Member] | Asset-backed securities, other
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	102	[1]	103	[1]
Significant Unobservable Inputs Readily Available [Member] | State and political subdivisions
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	47	[1]	48	[1]
Significant Unobservable Inputs Readily Available [Member] | Discounted cash flows | Derivative instruments, liabilities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative instruments, other, liabilities	9		9
Significant Unobservable Inputs Readily Available [Member] | Discounted cash flows | Asset-backed securities, student loans
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	14		12
Significant Unobservable Inputs Readily Available [Member] | Discounted cash flows | Asset-backed securities, credit cards
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	24		67
Significant Unobservable Inputs Readily Available [Member] | Discounted cash flows | Asset-backed securities, other
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	102		103
Significant Unobservable Inputs Readily Available [Member] | Discounted cash flows | State and political subdivisions
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Available-for-sale securities	47		48
Significant Unobservable Inputs Readily Available [Member] | Option model | Derivative instruments, liabilities
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative instruments, foreign exchange contracts, liabilities	153		106
Significant Unobservable Inputs Readily Available [Member] | Option model | Derivative instruments, assets
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative instruments, foreign exchange contracts, assets	172		113

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