Goodwill and Other Intangible Assets (Other intangible assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended							0 Months Ended		0 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Noncompete Agreements [Member]	Dec. 31, 2010 Noncompete Agreements [Member]	Dec. 31, 2011 Customer Relationships [Member]	Dec. 31, 2010 Customer Relationships [Member]	Dec. 15, 2011 Noncompete Agreements [Member] Months	Dec. 31, 2011 Noncompete Agreements [Member]	Dec. 15, 2011 Customer Relationships [Member] Years	Dec. 31, 2011 Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Amortization Period (in years or months)				46 months	27 months	9 years	5 years
Gross Carrying Amount				$ 30	$ 25	$ 121	$ 64
Accumulated amortization				25	24	43	36
Net amount				5	1	78	28
Acquired intangible assets									4		56
Acquired intangible assets, weighted average life (in years or months)								55		11.6
Amortization expense	8	7	8
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2012	12
2013	12
2014	10
2015	9
2016	8
Thereafter	32
Total	$ 83