Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accrued Liabilities (Details) [Abstract]
Accrued insurance costs	$ 124,499	$ 123,649
Deferred revenue	43,577	46,747
Accrued compensation	51,715	44,967
Taxes other than income	27,656	25,457
Accrued interest payable	3,580	4,422
Accrued restructuring costs	1,730	7,737
Accrued dividends	12,188	9,466
Accrued capital lease obligations	0	105
Accrued other	44,121	36,169
Total accrued liabilities	$ 309,066	$ 298,719