Accounting Policies (Details) (USD $)	12 Months Ended				12 Months Ended						3 Months Ended
	Dec. 31, 2012 units	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 Minimum [Member] Software and Software Development Costs [Member]	Dec. 31, 2012 Minimum [Member] Building Improvements [Member]	Dec. 31, 2012 Minimum [Member] Equipment [Member]	Dec. 31, 2012 Maximum [Member] Software and Software Development Costs [Member]	Dec. 31, 2012 Maximum [Member] Building Improvements [Member]	Dec. 31, 2012 Maximum [Member] Equipment [Member]	Dec. 31, 2012 Other Income [Member]
Property, Plant and Equipment [Line Items]
Pretax Gain Loss Recognized											$ 52,000,000
Fair Value of Total Borrowings	900,000,000
Market value of investments	760,000,000	835,000,000	1,416,000,000	1,118,000,000
Deferred technology costs, gross	115,000,000	90,000,000
Accumulated amortization of deferred technology costs	58,000,000	37,000,000
Number of operating segments	4
Property, plant and equipment useful life					3 years	15 years	2 years	7 years	40 years	10 years
Cost of advertisement	$ 34,000,000	$ 32,000,000	$ 30,000,000