Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Information about Litigation Matters
Number of Vendors, EPA Compliance Issue	1
Letters of Credit
Letters of Credit Outstanding, Amount	$ 60.1
Letter of credit outstanding outside of the Senior credit facility	5.0
New Store Construction Projects [Member]
Construction Commitments
Property and construction commitments	3.1
Property for Facilities Under Development [Member]
Construction Commitments
Property and construction commitments	13.3
Store Previously Under Lease [Member]
Construction Commitments
Property and construction commitments	$ 0.5
Number of stores, commitment to purchase	1