Acquisitions (Details 1) (Oakleaf [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Preliminary allocation of the purchase price to intangible assets
Total intangible assets subject to amortization	$ 87
Total intangible assets subject to amortization, weighted average amortization period	10 years 6 months
Customer relationships [Member]
Preliminary allocation of the purchase price to intangible assets
Total intangible assets subject to amortization	74
Total intangible assets subject to amortization, weighted average amortization period	10 years
Vendor relationships [Member]
Preliminary allocation of the purchase price to intangible assets
Total intangible assets subject to amortization	4
Total intangible assets subject to amortization, weighted average amortization period	10 years
Trademarks [Member]
Preliminary allocation of the purchase price to intangible assets
Total intangible assets subject to amortization	$ 9
Total intangible assets subject to amortization, weighted average amortization period	15 years