Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Commitments and Contingencies( Details) [Abstract]
Rental expense	$ 230,300,000	$ 221,900,000	$ 219,000,000
Future Minimum Rental Payment under Operating Leases (Table Details) [Abstract]
2012	185,394,000
2013	150,744,000
2014	117,040,000
2015	81,439,000
2016	41,020,000
Thereafter	6,671,000
Operating lease payments, total	582,308,000
Guarantor Obligations [Line Items]
Maximum financing amount	45,000,000
Amount outstanding	21,900,000
Investment in Equipment under Capital Leases (Table Details) [Abstract]
Equipment under capital lease	2,773,000	4,656,000
Accumulated amortization	(2,689,000)	(3,803,000)
Equipment under capital lease, net	84,000	853,000
Citibank [Member]
Guarantor Obligations [Line Items]
Maximum financing amount	25,000,000
Texas Capital Bank [Member]
Guarantor Obligations [Line Items]
Maximum financing amount	$ 20,000,000