Income Taxes (Unrecognized tax benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns, Net [Roll Forward]
Balance at January 1	$ 6	$ 6
Additions for tax positions of prior years	7	0
Additions for tax positions of prior years related to RSC acquisition	6	0
Settlements	(2)	0
Balance at December 31	$ 17	$ 6