Accrued Workers' Compensation Accrued Workers' Compensation (Schedule Of Amounts Recognized in Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accrued Workers' Compensation [Line Items]
Less amount included in accrued expenses	$ 10,371	$ 11,666
Noncurrent obligations	81,629	71,948
Occupational Disease [Member]
Accrued Workers' Compensation [Line Items]
Occupational disease costs	58,431	54,184
Workers' Compensation [Member]
Accrued Workers' Compensation [Line Items]
Occupational disease costs	33,569	29,430
Total obligations	92,000	83,614
Less amount included in accrued expenses	10,371	11,666
Noncurrent obligations	$ 81,629	$ 71,948