Schedule II Valuation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 29		$ 25		$ 23
Charged to Costs and Expenses	21		21		16
Deductions	17	[1]	17	[1]	14	[1]
Balance at End of Period	33		29		25
Reserve for Obsolescence and Shrinkage [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	1		1		1
Charged to Costs and Expenses	5		6		7
Deductions	4	[2]	6	[2]	7	[2]
Balance at End of Period	2		1		1
Self-Insurance Reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	93		83		86
Charged to Costs and Expenses	65		94		99
Deductions	75	[3]	84	[3]	102	[3]
Balance at End of Period	$ 83		$ 93		$ 83

[1] Represents write-offs of accounts, net of recoveries.

[2] Represents write-offs.

[3] Represents payments.