Investment Securities (Investment) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investment [Line Items]
Investments	$ 43,662	$ 48,439
Domestic Corporate Debt Securities [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		20,233
Debt securities, Gross unrealized gains	2,323	4,201
Debt securities, Gross unrealized losses	(217)	(302)
Domestic Corporate Debt Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	19,600
Domestic Corporate Debt Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Debt securities, Estimated fair value	21,706	24,132
US States and Political Subdivisions Debt Securities [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		4,084
Debt securities, Gross unrealized gains	235	575
Debt securities, Gross unrealized losses	(191)	(113)
US States and Political Subdivisions Debt Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	4,245
US States and Political Subdivisions Debt Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Debt securities, Estimated fair value	4,289	4,546
Residential Mortgage Backed Securities [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		2,198
Debt securities, Gross unrealized gains	139	183
Debt securities, Gross unrealized losses	(48)	(119)
Residential Mortgage Backed Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	1,819
Residential Mortgage Backed Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Debt securities, Estimated fair value	1,910	2,262
Commercial Mortgage Backed Securities [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		2,930
Debt securities, Gross unrealized gains	188	259
Debt securities, Gross unrealized losses	(82)	(95)
Commercial Mortgage Backed Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	2,929
Commercial Mortgage Backed Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Debt securities, Estimated fair value	3,035	3,094
Asset-backed Securities [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		5,784
Debt securities, Gross unrealized gains	60	31
Debt securities, Gross unrealized losses	(46)	(77)
Asset-backed Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	7,373
Asset-backed Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Debt securities, Estimated fair value	7,387	5,738
Foreign Corporate Debt Securities [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		2,391
Debt securities, Gross unrealized gains	103	150
Debt securities, Gross unrealized losses	(86)	(126)
Foreign Corporate Debt Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	1,741
Foreign Corporate Debt Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Debt securities, Estimated fair value	1,758	2,415
Foreign Government Debt Securities [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		1,617
Debt securities, Gross unrealized gains	81	149
Debt securities, Gross unrealized losses	(7)	(3)
Foreign Government Debt Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	2,336
Foreign Government Debt Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Debt securities, Estimated fair value	2,410	1,763
US Treasury and Government [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		3,462
Debt securities, Gross unrealized gains	45	103
Debt securities, Gross unrealized losses	(27)	0
US Treasury and Government [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	752
US Treasury and Government [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Debt securities, Estimated fair value	770	3,565
Retained Interest [Member]
Investment [Line Items]
Retained interests and AFS securities, Amortized cost		76
Retained interests, Gross unrealized gain	8	7
Retained interests, Gross unrealized loss	0	0
Retained Interest [Member] | Amortized Cost [Member]
Investment [Line Items]
Retained interests and AFS securities, Amortized cost	64
Retained Interest [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Retained interests, Estimated fair value	72	83
Available-for-sale Securities [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost		513
Retained interests, Gross unrealized gain	51	86
Available-for-sale Equity Securities, Gross Unrealized Loss	(3)	(3)
Available-for-sale Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Debt and AFS securities, Amortized cost	203
Available-for-sale Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Available-for-sale Securities, Equity, Estimated fair value	251	596
Trading Securities [Member]
Investment [Line Items]
Trading Securities		245
Trading Securities, Unrealized Holding Gain	0	0
Trading Securities, Unrealized Holding Loss	0	0
Trading Securities [Member] | Amortized Cost [Member]
Investment [Line Items]
Trading Securities	74
Trading Securities [Member] | Estimated Fair Value [Member]
Investment [Line Items]
Trading Securities	74	245
Total [Member]
Investment [Line Items]
Marketable Securities		43,533
Retained interests, Gross unrealized gain	3,233	5,744
Retained interests, Gross unrealized loss	(707)	(838)
Total [Member] | Amortized Cost [Member]
Investment [Line Items]
Marketable Securities	41,136
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Investment [Line Items]
Investments	686
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment [Line Items]
Investments	$ 1,224