Basis of Presentation Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012 Software and Software Development Costs [Member]	Dec. 31, 2012 Accumulated amortization [Member]
Prior Period Reclassification Adjustment	$ 170	$ 123	$ 30