Schedule II - Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Allowance for doubtful accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 33		$ 29		$ 25
Acquired	13		0		0
Charged to Costs and Expenses	37		21		21
Deductions	19	[1]	17	[1]	17	[1]
Balance at End of Period	64		33		29
Reserve for obsolescence and shrinkage [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	2		1		1
Acquired	1		0		0
Charged to Costs and Expenses	13		5		6
Deductions	13	[2]	4	[2]	6	[2]
Balance at End of Period	3		2		1
Self-insurance reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	83		93		83
Acquired	21		0		0
Charged to Costs and Expenses	84		65		94
Deductions	91	[3]	75	[3]	84	[3]
Balance at End of Period	$ 97		$ 83		$ 93

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

[2] Represents write-offs.

[3] Represents payments.